Theoretical Study on the Excited Electronic States of CHCl: Application

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Theoretical Study on the Excited Electronic States of CHCl#Application to Photodissociation at 193nm Shimin Shan, Xiamei Zhang, Erping Sun, Haifeng Xu, and Bing Yan J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.5b07543 • Publication Date (Web): 28 Sep 2015 Downloaded from http://pubs.acs.org on September 29, 2015

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The Journal of Physical Chemistry

Theoretical Study on the Excited Electronic States of CHCl：：Application to Photodissociation at 193nm

Shimin Shan 1,2, Xiaomei Zhang 1,2, Erping Sun 3, Haifeng Xu 1,2 *, Bing Yan 1,2 * 1

Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012,

China 2

Jilin Provincial Key Laboratory of Applied Atomic and Molecular

Spectroscopy (Jilin University), Changchun 130012, China 3

College of Electronic, Communication and Physics, Shandong University of

Science and Technology, Qingdao 266590, China

* Corresponding authors: Tel: 86-431-85168817; Fax: 86-431-85168816; Email: [email protected] (Haifeng Xu) and [email protected] (Bing Yan)

ACS Paragon Plus Environment


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ABSTRACT: We present herein a high-level ab initio study on the electronic excited states of the CHCl using internally contracted multireference configuration interaction method including Davidson correction (icMRCI+Q). A total of 13 electronic states with energy up to 7 eV have been investigated. The vertical transition energies, the oscillator strengths, electron configurations and transitions of electronic states of CHCl have been calculated at the icMRCI+Q/aug-cc-pv(5+d)Z level. The potential energy curves of the electronic states have been studied along the H-C-Cl angle, the C-H bond length and the C-Cl bond length, respectively. Our theoretical study has provided comprehensive information for understanding the interaction and the behavior of the electronic excited states of CHCl. Particularly, the excited state involved in the 193-nm photodissociation as well as the corresponding dissociation dynamics have been discussed based on our calculation results. The present study should shed more light on the photochemistry of CHCl in the ultraviolet region. Key Words：：CHCl; Multireference configuration interaction; Electronic excited state; Photodissociation dynamics


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INTRODUCTION Halocarbenes are important intermediates of photolysis of chlorofluorocarbons and halons, and play a crucial role in the chemical processes in the stratosphere, plasma and organic reactions.1 Information about the structure and behavior of their electronic excited states is essential to understand the mechanism of the reactions involving halocarbenes. On the other hand, due to various different nonadiabatic interactions between electronic excited states, the corresponding spectroscopy and dissociation of halocarbenes in the ultraviolet region are quite complicated, which have been an attractive research topic during the past several decades.2-7 The electronic spectroscopy, structure and dissociation dynamics of a variety of halocarbenes, such as CHX,8-13 CFX,14-18 CX219-23 (X = F, Cl, Br, I), have been investigated by numerous studies using laser-based high-resolution experimental techniques as well as high-level theoretical calculations. The study presented here focuses on the electronic excited states of CHCl. Following the first reported rotationally resolved absorption spectra for the CHCl A1A'' ← X1A' system in 1966,24 the spectroscopy of CHCl was substantially investigated.25-32 Most studies were carried out on the ground electronic state X1A', the first excited singlet state A1A'' and the lowest triplet state a3A''. For example, Sears et al25-27 reported the near-infrared spectrum of CHCl using the frequency-modulation

transient

absorption

technique

and

laser

absorption

spectroscopy; Tao et al31 investigated the A1A''←X1A' transition of CHCl using fluorescence excitation and single vibronic level emission spectroscopy; In addition, there are many theoretical studies were performed on the geometries and vibrational frequencies of the states, as well as singlet-triplet gap (∆ES-T) of CHCl using different calculation methods.12, 33 Little information is available for the electronic excited states higher than the A1A'' state of CHCl. The spectroscopy and dynamics of the S2 (21A') state of CHCl and its deuterated isotopomer were studied using optical-optical double resonance technique, indicating the state is a predissociative state.28 The geometric parameters, harmonic frequencies and energy of the S2 state of CHCl and its deuterated



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isotopomer were calculated at MRCI+Q/CBS level.28 In 2008, Shin and Dagdigian

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carried out an experimental study on the photodissociation of CHCl at 193-nm. The CH fragment from the 193-nm photodissociation of CHCl was observed, and the internal energy distribution was determined by analysis of the laser induced fluorescence (LIF) spectra of the CH fragment. It was predicted that the dissociation occurs through a nonlinear excited state of CHCl according to the experimental observations. However, the excited states that could be involved in the photodissociation as well as the corresponding dynamics remain unknown, owing to the lack of accurate information about the electronic excited states of CHCl. In order to add our knowledge on structure and behavior of the high-lying excited states, and to shed more light on the photodissociation dynamics in the ultraviolet region, we carried out a high-level ab initio study on a total of 13 electronic states of the CHCl, using the internally contracted multireference configuration interaction method with Davidson correction (icMRCI+Q). The vertical transition energy, oscillator strength, electron configuration and transition of the electronic states of CHCl were reported. The potential energy curves (PECs) of the electronic states were calculated along the H-C-Cl bond angle, the C-H bond length and the C-Cl bond length, respectively. Based on our calculation results, the interaction between the excited states, and the mechanism of photodissociation at 193-nm were discussed. The results in the present study could be valuable for further experimental measurements of the photochemical processes of the CHCl. METHODS Calculation was performed on the excited states using full-valence complete active space multiconfiguration self-consistent field (CASSCF)34 and internally contracted singly and doubly excitation multireference configuration interaction (icMRCISD) method35 with Davidson correction36 to account for high-order excitation configurations. The molecular orbitals and energies of the ground state were first calculated through the Hartree-Fock (HF) self-consistent field method. The CASSCF calculations were carried out for the orbital optimization by using the HF MOs as the starting orbitals. Further, by utilizing all configurations in the


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configuration interaction (CI) expansion of the CASSCF wave functions as reference wave functions, the energies were obtained by icMRCI+Q method. The active space consists of 12 active electrons and 9 active orbitals corresponding to n=1 atomic orbital of H atom, n=2 atomic orbital of C atom and n=3 orbital of Cl. The correlation consistent basis sets aug-cc-pVXZ (X=T, Q, 5)37 for hydrogen and carbon, were used in ab initio calculation. The similar basis set including tight-d functions, aug-cc-pV(X+d)Z,38 was employed for the chlorine. We performed calculation on the geometry optimization and the harmonic vibrational frequencies of the ground state (X1A'), the first excited singlet state (A1A'') and the lowest triplet state (a3A'') at aug-cc-pV(Q+d)Z level. Besides, the extrapolation to CBS limit was performed for the lowest three states using the formula 2

E = Ecbs + Be−(n−1) + Ce−(n−1) . n=3, 4, 5 were used to determine the Ecbs value. The scalar

relativistic effect and core-valence correlations were considered in the calculation. The scalar relativistic effect was obtained with third-order Douglas-kroll approximation39,

40

with the aug-cc-pVTZ-Dk37 basis sets. The core-valence

corrections of the n=2 shell for Cl were performed at icMRCI+Q/aug-cc-pwCVTZ level.41, 42 The energy convergence threshold is 10-10 hartree; the gradient convergence threshold in geometry optimization is 10-4 a.u. The harmonic vibrational frequencies were determined employing the method mentioned above at icMRCI+Q/ aug-cc-pV(Q+d)Z level. The one-dimensional potential energy cuts of 13 electronic states of CHCl were given at the icMRCI+Q/ aug-cc-pV(T+d)Z level along the angel of H-C-Cl, the C-H and C-Cl bond lengths, respectively, with the other two parameters fixed at their respective equilibrium values of the ground state. The vertical transition energies (VTE) and oscillator strengths for different excited states to ground state were obtained at icMRCI/aug-cc-pV(5+d)Z level. All calculations were carried out employing the MOLPRO2010 software package.43 RESULT AND DISCUSSION A. Vertical Transition Energies, Equilibrium Geometries and Harmonic Vibrational Frequencies of the Electronic Excited States of CHCl



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The purpose of the present study is to add our understanding of the electronic excited states of CHCl and particularly to shed more light on the photodissociation dynamics at 193 nm. We calculated a total of 13 electronic states of CHCl with VTE up to 7 eV, about 0.57 eV higher than the photon energy of the 193-nm light (hν193). Table 1 lists the VTE, the oscillator strength (OS), the main electronic configuration and the corresponding transition of each electronic state of CHCl calculated at the icMRCI+Q/aug-cc-pv(5+d)Z level. There are eight electronic states with VTE lower than 5.6 eV, including the ground state X1A' (11A'), three singlet excited states (11A'', 21A' and 21A'') and four triplet states (13A'', 13A'', 23A'' and 23A'). It can be seen that the spin-allowed transitions from the ground 11A' state to the three singlet excited states lie at VTE more than 1 eV lower than hν193, thus will have little contribution in the photodissociation of CHCl at 193 nm. The electronic excited state with the largest oscillator strength is the 41A' state. The VTE of 41A' is 6.42 eV with consideration of the zero-point energy, which is only 0.004 eV smaller than hν193. This state arises from the electronic configurations of (1-2a'')2(9a')2(10a')(11a') and (2a'')(9-10a')2(3a''), corresponding to 10a'→11a' (62.6%) and 2a''→3a'' (14.4%) transitions. For the 31A' state that is 0.54 eV lower than the 41A' state, it could be possible to be populated in its vibrational excited states upon absorption of the 193-nm light, however, the oscillator strength is about an order of magnitude smaller than that of the 41A' state. The other optical-bright excited state, the 31A'' state is 0.43 eV above the 41A' state, and has the smallest oscillator strength that is as much as three orders of magnitude smaller than that of the 41A' state. The results strongly indicate that the 41A' state is the initial populated excited state in 193-nm photodissociation of CHCl. It should be mentioned that two triplet states (33A'' and 33A') that are spin-forbidden transitions from the ground state, lie close to the 41A' state, thus may play important role in the 193-nm photodissociation dynamics. In Table 2, we present the equilibrium geometries and the harmonic vibrational frequencies of the 41A' state calculated at the icMRCI+Q/ aug-cc-pV(Q+d)Z level. To date there is neither experimental nor theoretical results of the 41A' state in the


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literature. In order to show the accuracy of our calculations, we include in the table our results of the ground state X1A', the first excited singlet state 11A'' (A1A'') and the lowest triplet state 13A'' (a3A''), and compare with the available experimental and theoretical results in the literature. As shown in the table, our high-level icMRCI+Q calculations of these three states are well consistent with the experimental results and previous calculations in the literature. We also investigated the effect of different basis, scalar relativistic effect (SR) and the Core-Valence (CV) correction on the calculated geometries of the X1A'，A1A'' and a3A'' states (see Table S1 in the Supporting Information). The results indicate that the correlation effects have little influence on the geometries of CHCl, thus were not considered in the calculation of the 41A' state. It can be seen from the table that the bond lengths of the X1A'，A1A'' and a3A'' states are close, while the bond angle of the A1A'' or a3A'' state is more than 20° larger than that of the ground state, which is due to transition of at least one nonbonding electron to an out-plane P orbital of carbon. On the other hand, the C-Cl bond length of the 41A' state changes significantly, which is more than 0.5 Å larger than that of the ground state, indicating much weaker bonding between the C and Cl atoms. The C-H bond length is 1.148 Å, which is similar with that of the lower electronic states. It should be mentioned that the calculated C-H bond length of the 41A' state of CHCl is only 0.018 Å larger than that of the CH(X2Π) radical (1.13±0.04 Å).45 This indicates that there could be little vibrational excitation of the CH(X2Π) fragment through dissociation along the 41A' state of CHCl. Indeed, the degree of the vibrational excitation of the CH fragment was observed to be only about 3.5% of the total available energy in experimental study of photodissociation at 193nm.7 The bond angle of the 41A' state is 83°, about 20° smaller than that of the ground state and more than 43° smaller than that of the A1A'' or a3A'' state, due to the main transition of 10a'-11a' that corresponds to excitation of nonbonding electrons of Px and Pz orbitals to empty Pz orbital. B. Potential Energy Curves of the Electronic Excited States of CHCl



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The rigid one-dimensional potential energy curves (PECs) of the electronic states of CHCl along the H-C-Cl bond angle, C-H bond length and the C-Cl bond length were calculated at the icMRCI/ aug-cc-pV(T+d)Z level, and the results are presented in Figure 1-3 respectively. In each figure, the other two geometric parameters were fixed at their respective equilibrium values in ground state. Besides the X1A', a3A'' and A1A'' states, other excited states, 23A', 41A', 33A'', 33A' and 31A'', are also bent states (Figure 1). The 21A' state is a quasi-linear state with an energy minimum at a H-C-Cl angle of about 166°, which is consistent with results of previous study by Tao and co-workers.28 The other states, 23A'', 13A', 21A'' and 31A', are linear structure. Avoided crossing points between different states can be found in bending potentials, such as 21A''-31A'' states at 145°, 31A'-41A' states at 75° and 13A'-23A' states at 120°, which indicate the presence of strong coupling in these conical intersection regions. The dissociation limits that are related to the electronic states of CHCl studied in this study are presented in Table 3, including six “CCl + H” channels and two “CH + Cl” channels. The PECs along C-H bond length of the 13 electronic states of CHCl are shown in Figure 2. All the states are bound, except that the 13A' state is weakly bound at around RCH=1.1 Å but turns to become dissociative at RCH larger than 1.38 Å. In the triplet manifold, the 13A' state crosses with the bound 23A' and 23A'' states at RCH= 1.37 Å and 1.49 Å, respectively, leading to dissociation to the CCl(X2Π) + H(2Sg) channel. The 13A' state also crosses with the singlet state, 21A', at RCH= 1.44 Å. Thus, the optical-bright 21A' state (VTE = 4.23 eV) could predissociate along the C-H bond due to the spin-orbit interaction with the 13A' state. For other optical-bright states with VTE higher than that of the 21A' state, there are no such interactions. Note that these states are all associated with “CCl + H” dissociation limits≥8 eV and have potential well larger than 1.5 eV. Our results strongly indicate that the “CCl + H” dissociation channel is negligible with the excitation photon energy of 5-8 eV. The PECs along C-Cl bond length (Figure 3) are quite different from those along the C-H bond length (Figure 2). In the singlet manifold, the ground state X1A' and the first excited singlet state A1A'' are typically bound along the C-Cl bond with deep


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potential wells, while the 21A'' and 31A'' states are repulsive states. The 21A' and 31A' states are weakly bound at around Rccl=1.65 Å and 1.83 Å, respectively, but tend to repulsive at long R distance. Dissociation barriers are observed in these two states along the C-Cl bond, which are attributed to the avoided crossing between 21A' and 31A' at Rccl=1.90 Å, and 31A' and 41A' at Rccl=2.05 Å, respectively. The 41A' state, which has a potential well of 1.2 eV at the internuclear distance Rccl=2.05 Å, is adiabatically related to the higher dissociation limit CH(A2∆) + Cl (2Pu), while all the other singlet states are related to the lower dissociation limit CH(X2Π) + Cl(2Pu). However, the interactions between 41A' and other states will result in dissociation to the CH(X2Π) + Cl(2Pu) channel. In addition, all the triplet states except a3A'' are almost purely repulsive, leading to the lowest dissociation channel CH(X2Π) + Cl(2Pu). These repulsive triplet states may also interact with the singlet excited states through spin-orbit coupling. The predissociation mechanism of the 41A' state will be further discussed in the following section. C .Discussion of the photodissociation mechanism of CHCl at 193nm As we have clearly shown in the previous sections, the 41A' state with VTE of 6.42 eV is the initial state of CHCl that is excited by 193nm laser fields. Our calculated PECs in Figure 2 and Figure 3 indicate that photodissociation from the 41A' state should produce the “CH + Cl” channel, while the “CCl + H” channel is negligible, confirming the experimental study by Shin and Dagdigian7 in which the CCl fragment has not been observed. In this section, we will discuss the mechanism of the 41A' state to dissociate to the “CH + Cl” channel based on our high-level ab initio calculation. According to the calculated bond angle of the 41A' state (Table 2), we could estimate the rotational distribution of the CH fragment using the modified impulsive model46

E ROT / E AVL

mH .mCl sin 2 θ = (mC + mCl )(mC + mH ) − mH mCl cos2 θ

Here, the EROT is the rotational energy of diatomic photofragment CH, the EAVL is the total available energy, mC , mCCl and mH are the mass of the C, Cl and H atoms,



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respectively. The EROT/EAVL ratio is estimated to be only 5.7% in this study, in good agreement with the experimental measured value of 7.5%.7 In addition, our calculated C-H bond length of CHCl (41A') is close to that of the CH (X2Π) radical, suggesting low vibrational excitation of CH fragment after dissociation, which also confirms the observation in experimental study.7 Our calculated PEC of the 41A' state along the C-Cl bond shows that the state is bound with a potential well of 1.2 eV at Rccl=2.05 Å. This potential well is attributed to the avoided crossing between the 41A' and 31A' states (Figure 3). The 41A' state is associated with the excited dissociation limit CH(A 2∆) + Cl(2Pu) at 6.9 eV. However, strong perturbation by nearby singlet and the triplet states along the C-Cl bond distance may lead the 41A' state to dissociate to the lowest dissociation limit CH(2Π) + Cl(2Pu) indirectly. In order to shed more light on the corresponding predissociation dynamics, we present in Figure 4 the PECs of the 41A' state along with those states that could interact with 41A', including singlet states (31A' and 31A'') and triplet states (33A' and 33A''). The vertical transition to 41A' by the 193-nm laser is also indicated in the figure. The 41A' state could be coupled to the repulsive triplet states 33A'' and 33A' by the spin-orbit interaction. The crossing point of 41A'-33A'' is located at Rccl=1.75 Å, very close to the Franck-Condon (FC) region of the 193-nm excitation from the ground electronic state, while that of 41A'-33A' is located at about 0.5 Å away from the FC region. We calculated the spin−orbit matrix element with the aid of the BP operator.47 The resulting values are ～64 cm-1 for 41A'-33A'' and only ～14 cm-1 for 41A'-33A', indicating much stronger interaction between 41A' and 33A'' states . The singlet 31A' state has the same symmetry as 41A', thus an avoided crossing can be clearly seen between the PECs of the two states. We computed the nonadiabatic coupling matrix element as a function of the C-Cl bond distance at the CASSCF/AVTZ level of theory (see Figure S1 in the Supporting Information), and found strong coupling of 41A'-31A' near Rccl=2.05 Å, indicating strong adiabatic coupling exists in the conical intersection between 31A' state and 41A' state. On the other hand, although the 41A' state also crosses with the singlet 31A'' state at Rccl=2.07 Å, the coupling between them should be much weaker because of their different


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symmetry. Moreover, the coupling between the 41A' and the 31A'' states occurs through Coriolis interaction, which should be weak due to the small rotational angular momentum of the parent CHCl observed in the experiment of Shin and Dagdigian7. The above analysis indicates that the spin-orbit coupling of 41A'-33A'' and the avoided crossing between 41A'-31A' may play significant roles in the predissociation of CHCl at 193-nm. In the present study, it is however unlikely to further determine which coupling is the dominant process. However, the experimental observation by Shin and Dagdigian7 shows that the CH fragment prefers to be populated at the Λ-doublet state of A'' symmetry and appears to be more pronounced at high rotational states, thus strongly indicates that the dissociation of CHCl occurs through a nonlinear excited states with A'' symmetry. It is noted that the 31A' state is linear while the 33A'' state is a bent state (see Figure 1). Therefore, after excitation to the 41A' state by absorption of hν193, there is large probability to interact with the nonlinear triplet state 33A'' through spin-orbit coupling, and finally the CHCl molecule could dissociate along 33A'' to produce CH(2Π) + Cl(2Pu) products. Our study indicates the spin-orbit coupling could be important in predissociation of polyatomic molecules. Further studies should be necessary to perform ultrafast time-resolved measurements to give more information on the dissociation dynamics of CHCl. CONCLUSION In this work, we performed a high-level ab initio study on the electronic excited states of the CHCl. A total of 13 electronic states of CHCl with vertical transition energy (VTE) up to 7 eV were investigated. The VTE, oscillator strength, electron configuration and transition of electronic states of CHCl were reported. It is shown that the 41A' state is the initial excited state in 193-nm photodissociation of CHCl. The equilibrium geometries and the harmonic vibrational frequencies of 41A' was calculated at the icMRCI+Q/ aug-cc-pV(Q+d)Z level. To explore the properties of the electronic excited states of CHCl, and particularly to understand dissociation dynamics of CHCl at 193-nm, we examined the PECs of the electronic states along the H-C-Cl bond angle, the C-H bond length, and the C-Cl bond length, respectively. Based on our study, the interaction of the 41A' state with other electronic excited



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states was discussed. It is strongly indicate that the CH(2Π) + Cl channel is the main products at 193-nm, which may be produced through the 41A'-33A'' interaction. Our theoretical results support the experimental observations in the literature and shed more light on the photodissociation dynamics of CHCl at 193nm. The present study also adds our understanding on the behavior of the electronic excited states of CHCl in the ultraviolet region, and could be valuable for further experimental studies on CHCl.

ASSOCIATED CONTEN Supporting Information The effect of different basis, scalar relativistic effect (SR) and the Core-Valence (CV) correction on the calculated geometries of the X1A'，A1A'' and a3A'' states；The nonadiabatic coupling matrix element as a function of the C-Cl bond distance calculated at the CASSCF/AVTZ level of theory, for the avoided crossing between the PECs of 41A'-31A' states and 31A'-21A' states. ACKNOWLEDGMENTS This work was supported by National Basic Research Program of China (973 Program) (Grant No. 2013CB922200), National Natural Science Foundation of China (Grant Nos. 11534004, 11574114, U1532138, 11274140) and Natural Science Foundation of Jilin Province (Grant No. 20150101003JC). The High Performance Computing Center (HPCC) of Jilin University for supercomputer time is acknowledged. REFERENCE (1) Kable, S. H.; Reid, S. A.; Sears, T. J. The halocarbenes: Model Systems for Understanding the Spectroscopy, Dynamics and Chemistry of Carbenes. Int. Rev. Phys. Chem. 2009, 28, 435-480. (2) Morley, G.P.; Felder, P.; Robert Huber, J. Photodissociation of Dichlorocarbene CCl2 at 248 nm in a Cold Beam. Chem. Phys. Lett. 1993, 219, 195-199. (3) Shin, S. K.; Dagdigian, P. J. Dynamics of the 193 nm Photodissociation of Dichlorocarbene. J. Chem. Phys. 2006, 125, 133317.


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(4) Shin, S. K.; Dagdigian, P. J. Photodissociation Dynamics of Dichlorocarbene at 248 nm. Phys. Chem. Chem. Phys. 2006, 8, 3446-3452. (5) Shin, S. K.; Dagdigian, P. J. Further Investigation of the Photodissociation Dynamics of Dichlorocarbene near 248 nm. J. Chem. Phys. 2008, 128, 154322. (6) Shin, S. K.; Dagdigian, P. J. Internal State Distribution of the CF Fragment from the 193 nm Photodissociation of CFCl and CFBr. J. Chem. Phys. 2007, 126, 134302. (7) Shin, S. K.; Dagdigian, P. J. Formation of the CH Fragment in the 193 nm Photodissociation of CHCl. J. Chem. Phys. 2008, 128, 064309. (8) Richmond, C.; Tao, C.; Mukarakate, C.; Dawes, R.; Brown, E. C.; Kable, S. H.; Reid, S. A. Optical-optical Double Resonance Spectroscopy of the Quasi-Linear S2 State of CHF and CDF. II. Predissociation and Mode-Specific Dynamics. J. Chem. Phys. 2011, 135, 104316. (9) Tao, C.; Mukarakate, C.; Judge, R. H.; Reid, S. A. High Resolution Probe of Spin-Orbit Coupling and the Singlet-Triplet Gap in Chlorocarbene. J. Chem. Phys. 2008, 128, 171101. (10)

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Relativistic Multireference Configuration Interaction Investigation of Fluoroiodo Carbene. J. Phys. Chem. A. 2014, 118, 2447-2452. (16) Fernández, J. A. M., R.; Sánchez Rayo, M. N.; Castaño, F. Direct Measurements of Removal Rates of CFCl(X̃ 1A'(0,0,0)) and CFCl(X̃ 1A'(0,1,0)) by Simple Alkenes. J. Phys. Chem. A. 1996, 100, 12305-12310. (17) Knepp, P. T.; Scalley, C. K.; Bacskay, G. B.; Kable, S. H. Electronic Spectroscopy and ab initio Quantum Chemical Study of the Ã(1Aʺ)−X̃ (1Aʹ) Transition of CFBr. J. Chem. Phys. 1998, 109, 2220-2232. (18) Knepp, P. T.; Kable, S. H. The Photodissociation Dynamics of CFBr Excited into the Ã(1Aʺ) State. J. Chem. Phys. 1999, 110, 11789-11797. (19) Clouthier, D. J.; Karolczak, J. A Pyrolysis Jet Spectroscopic Study of the Rotationally Resolved Electronic Spectrum of Dichlorocarbene. J. Chem. Phys. 1991, 94, 1-10. (20) Hsu, H. J.; Chang, W. Z.; Chang, B. C. Dispersed Fluorescence Spectroscopy of the CBr2 Ã 1B1-X̃ 1A1 Transition. Phys. Chem. Chem. Phys. 2005, 7, 2468-2473. (21) Sendt, K.; Bacskay, G. B. Spectroscopic Constants of the X̃ (1A1), ã(3B1), and Ã(1B1) States of CF2, CCl2, and CBr2 and Heats of Formation of Selected Halocarbenes: An ab initio Quantum Chemical Study. J. Chem. Phys. 2000, 112, 2227-2238. (22) Chau, F.-T.; Dyke, J. M.; Lee, E. P. F.; Mok, D. K. W. Simulation of Ã 1B1→X̃ 1

A1 CF2 Single Vibronic Level Emissions: Including Anharmonic and Duschinsky

Effects. J. Chem. Phys. 2001, 115, 5816-5822. (23) Liu, M.-L.; Lee, C.-L.; Bezant, A.; Tarczay, G.; Clark, R. J.; Miller, T. A.; Chang, B.-C. Dispersed Fluorescence Spectra of the CCl2 Ã–X̃ Vibronic Bands. Phys. Chem. Chem. Phys. 2003, 5, 1352-1358. (24) Merer, A. J.; Travis, D. N. Absorption Spectra of HCCl and DCCl. Can. J. Phys. 1966, 44, 525-547. (25) Chang, B.-C.; Sears, T. J. Frequency-Modulation Transient Absorption Spectrum of the HCCl Ã 1Aʹʹ(0,0,0)←X̃

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Aʹ(0,0,0) Transition. J. Chem. Phys. 1995, 102,

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(26) Lin, A.; Kobayashi, K.; Yu, H.-G.; Hall, G. E.; Muckerman, J. T.; Sears, T. J.; Merer, A. J. Axis-Switching and Coriolis Coupling in the Ã(010)–X̃ (000) Transitions of DCCl and HCCl. J.Mol.Spectrosc. 2002, 214, 216-224. (27) Wang, Z.; Bird, R. G.; Yu, H. G.; Sears, T. J. Hot bands in Jet-Cooled and Ambient Temperature Spectra of Chloromethylene. J. Chem. Phys.2006, 124, 74314. (28) Tao, C.; Richmond, C. A.; Mukarakate, C.; Kable, S. H.; Bacskay, G. B.; Brown, E. C.; Dawes, R.; Lolur, P.; Reid, S. A. Spectroscopy and Dynamics of the Predissociated, Quasi-Linear S2 State of Chlorocarbene. J. Chem. Phys. 2012, 137, 104307. (29) Fan, H.; Ionescu, I.; Annesley, C.; Cummins, J.; Bowers, M.; Reid, S. A. Fluorescence Excitation Spectroscopy of the System of Jet-Cooled HCCl in the Region 5150–6050Å. J.Mol.Spectrosc. 2004, 225, 43-47. (30) Steimle, T. C.; Wang, F.; Zhuang, X.; Wang, Z. Optical Stark Spectroscopy of the Ã 1A''- X̃ 1A' Band of Chloro-Methylene, HCCl. J. Chem. Phys. 2012, 136, 114309. (31) Tao, C.; Mukarakate, C.; Reid, S. A. Fluorescence Excitation and Single Vibronic Level Emission Spectroscopy of the Ã 1A"←X̃ 1A' System of CHCl. J. Chem. Phys. 2006, 124, 224314. (32) Lin, C. S.; Chen, Y. E.; Chang, B. C. New Electronic Spectra of the HCCl and DCCl Ã-X̃ Vibronic Bands. J. Chem. Phys. 2004, 121, 4164-4170. (33) Tarczay, G.; Miller, T. A.; Czakó, G.; Császár, A. G. Accurate ab initio Determination of Spectroscopic and Thermochemical Properties of Mono- and Dichlorocarbenes. Phys . Chem. Chem. Phys. 2005, 7, 2881-2893. (34) Werner, H.-J.; Knowles, P. J. A Second Order Multiconfiguration SCF Procedure with Optimum Convergence. J. Chem. Phys. 1985, 82, 5053-5063. (35)

Werner,

H.-J.;

Knowles,

P.

J.

An

efficient

Internally

Contracted

Multiconfiguration–Reference Configuration Interaction Method. J. Chem. Phys. 1988, 89, 5803-5814. (36) Langhoff, S. R.; Davidson, E. R. Configuration Interaction Calculations on the Nitrogen Molecule. Int. J. Quantum Chem 1974, 8, 61-72. (37) Dunning Jr, T. H. Gaussian Basis Sets for Use in Correlated Molecular



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Calculations. I. The Atoms Boron Through Neon and Hydrogen. J. Chem. Phys. 1989, 90, 1007-1023. (38) Dunning Jr, T. H.; Peterson, K. A.; Wilson, A. K. Gaussian Basis Sets for Use in Correlated Molecular Calculations. X. The Atoms Aluminum Through Argon Revisited. J. Chem. Phys. 2001, 114, 9244-9253. (39) Reiher, M.; Wolf, A. Exact Decoupling of the Dirac Hamiltonian. I. General Theory. J. Chem. Phys. 2004, 121, 2037-2047. (40) Wolf, A.; Reiher, M.; Hess, B. A. The Generalized Douglas–Kroll Transformation. J. Chem. Phys. 2002, 117, 9215-9226. (41) Peterson, K. A.; Dunning, T. H. Accurate Correlation Consistent Basis Sets for Molecular Core–Valence Correlation Effects: The Second Row Atoms Al–Ar, and the First Row Atoms B–Ne Revisited. J. Chem. Phys. 2002, 117, 10548-10560. (42) Kendall, R. A.; Dunning, T. H.; Harrison, R. J. Electron Affinities of the First-Row Atoms Revisited. Systematic Basis Sets and Wave Functions. J. Chem. Phys. 1992, 96, 6796-6806. (43) Werner, H.-J.; Knowles, P. J.; Lindh, R.; Manby, F. R.; Schütz, M.; Celani, P.; Korona, T.; Mitrushenkov, A.; Rauhut, G.; Adler, T. B.; et al. MOLPRO, a Package of ab initio Programs, 2010. (44) Kakimoto, M.; Saito, S.; Hirota, E. Doppler-Limited Dye Laser Excitation Spectroscopy of HCCl. J. Mol. Spectrosc. 1983, 97, 194-203. (45) Zachwieja, M. New Investigations of the A 2∆- X 2Π Band System in the CH Radical and a New Reduction of the Vibration-Rotation Spectrum of CH from the ATMOS Spectra. J. Mol. Spectrosc. 1995, 170, 285-309. (46) Levene, H. B.; Valentini, J. J. The Effect of Parent Internal Motion on Photofragment Rotational Distributions: Vector Correlation of Angular Momenta and C2v Symmetry Breaking in Dissociation of AB2 Molecules. J. Chem. Phys. 1987, 87, 2594-2610. (47) Berning, A.; Schweizer, M.; Werner, H.-J.; Knowles, M. S.; Palmieri, P. Spin-Orbit Matrix Elements for Internally Contracted Multireference Configuration Interaction Wavefunctions. Mol. Phys. 2000, 98, 1823-1833.


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Page 17 of 22

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Table 1. VTE, Oscillator Strength, Electron Configuration, and Transition of Electronic States of CHCl Calculated at the icMRCI+Q/aug-cc-pV(5+d)Z level state

VTE a (ev)

X1A' (1 1A')

0

(2a'')2(9a')2(10a')2

a3A'' (1 3A'')

0.37

(2a'')2(9a')2(10a')3a''

1

1

A A'' (1 A'') 1

1.68

oscillator strength

0.00319

2

10a'→3a''(0.920)

2

(2a'') (9a') (10a')3a'' 2

2

10a'→3a''(0.934)

2

(10a')2→(3a'')2(0.898)

4.23

23A''

4.69

(8a')2 (2a'')2(9a')(10a') 2 (3a'')

9a'→3a''(0.883)

5.03

(2a'')(9-10a') 2 (3a'')

2a''→3a''(0.945)

1 A' 1

2 A''

5.10

3

2 A'

5.51

31A'

5.88

0.00404

(8a') (2a'') (9a') (3a'')

2

2 A' 3

0.00296

Excitation b

main configuration

2

2

(8a') (2a'') (9a')(10a') (3a'') 2

0.0139

2

2

(1-2a'') (9a') (10a')(11a')

10a'→11a'(0.843)

(1a'')2(2a'')(9-10a')2(3a'')

2a''→3a''(0.665)

2

2

10a'→11a'(0.191)

2

2

10a'→11a'(0.626)

(1-2a'') (9a') (10a')(11a') 1

4 A'

6.42

0.118

(1-2a'') (9a') (10a')(11a') (1a'')2(2a'')(9-10a')2(3a'')

3

3 A'' 3

3 A' 1

3 A''

2

6.55 6.85

2

2a''→3a''(0.144) 2

(7a') (8a') (2a'') (9-10a') (3a'') 2

6.63

2

(8a') (2a'') (9a')(10a') (3a'') 6.28 ×10

−4

9a'→3a''(0.835)

2

2

2

2

(7a') (8a') (2a'') (9-10a') (3a'') 2

2

(2a'')(9a') (10a') (3a'')

8a'→3a''(0.844) 9a',10a'→(3a'')2(0.900) 8a'→3a''(0.626) 10a',2a''→(3a'')2(0.227 )

a

The zero-point energy of the ground state was considered in the values of VTE.

b

The value in parentheses refers to the coefficient of the corresponding configuration.



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Page 18 of 22

Table 2. Equilibrium geometries and Harmonic vibrational frequencies of CHCl. state X1A'

RC-H (Å)

A A''

41A'

ω2 (cm-1)

ω3 (cm-1)

1.695

102.4

816

1223

2937

expt.

1.119[a]

1.696[a]

101.4[a]

830[b]

1229[b]

2942[ b]

1.093/1.11

1.719/1.707

103.1/101.8

798/831

1272/1229

3129/2919

1.083

1.629

131.34

888

933

3174

[c]

this work

calc.[c] a A''

ω1 (cm-1)

1.107

expt. 3

∠H-C-Cl (deg.)

This work

calc. 1

RC-Cl (Å)

this work

[d]

[d]

1.053

1.071/1.079 1.081

[d]

[d]

1.623

134.7

873

926

2980[b]

1.659/1.629

131/131.5

886.3/873

968/947

3358/3216

1.659

126.34

887

978

3199

[b]

[e]

[b]

expt.

-

-

-

886

972

3083[b]

calc.[c]

1.071/1.083

1.692/1.671

125.4/126.3

857/905

1052/985

3346/3229

this work

1.148

2.233

83

569.9

1303.2

2528

[a]

Ref. [44]. [b] Ref. [31]. [c] The results calculated with different methods in Ref. [12]. [d] Ref. [25]. [e]Ref. [27].

Table 3. The adiabatic dissociation channels, energies and the corresponding electronic states Dissociation channel

Energy of dissociation limit (eV)

Electronic states

“CCl + H” CCl (X2Π) + H (2Sg)

3.6

11A', 11A'',13A' and 13A''

CCl (a4Σ-) + H (2Sg)

6.0

23A''

CCl (A2∆) + H (2Sg)

8.1

21A' ,21A'',23A' and 33A''

CCl ( b4∆)+ H (2Sg)

8.3

33A'

CCl ( B2∆) + H (2Sg)

8.8

31A' and 31A''

CCl ( C2Σ+)+ H (2Sg)

9.3

41A'

“CH + Cl” CH ( X 2Π) + Cl (2Pu)

4.03

11A',11A'',21A',21A'',31A',31A'', 13A',13A'',23A',23A'',33A' and 33A''

CH ( A2∆) + Cl (2Pu)

6.9

41A'


Page 19 of 22

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Figure Captions: Figure 1. Potential energy curves of CHCl with respect to the H-C-Cl angle calculated at the icMRCI+Q/aug-cc-pV(T+d)Z level. The C-Cl and the C-H bond lengths were fixed at their respective equilibrium values.

Figure 2. Potential energy curves of CHCl with respect to the C-H bond calculated at the icMRCI+Q/aug-cc-pV(T+d)Z level. The C-Cl bond length and the H-C-Cl angle were fixed at their respective equilibrium values.

Figure 3. Potential energy curves of CHCl with respect to the C-Cl bond calculated at the icMRCI+Q/aug-cc-pV(T+d)Z level. The C-H bond length and the H-C-Cl angle were fixed at their respective equilibrium values

Figure 4. Potential energy curves of selected states along the C-Cl bond calculated at the icMRCI+Q/aug-cc-pV(T+d)Z level.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 1

Figure 2


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Figure 3

Figure 4



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TOC GRAPHIC


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Theoretical Study on the Excited Electronic States of CHCl: Application

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