LETTER pubs.acs.org/JPCL
Photodetachment of Isolated Bicarbonate Anion: Electron Binding Energy of HCO3 Xue-Bin Wang*,†,‡ and Sotiris S. Xantheas*,† †
Chemical & Materials Sciences Division, Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MS K1-83, Richland, Washington 99352, United States ‡ Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99354, United States ABSTRACT: We report the first direct photodetachment photoelectron spectroscopy of HCO3 in the gas phase under lowtemperature conditions. The observed photoelectron spectra are complicated due to excitations of manifolds in both vibrational and electronic states. A long and single vibrational progression with a frequency of 530 ( 20 cm1 is partially resolved in the threshold of the T = 20 K, 266 nm spectrum. The adiabatic electron detachment energy (ADE) of HCO3, or, in other words, the electron affinity (EA) of neutral HCO3, is experimentally determined from the (0,0) transition to be 3.680 ( 0.015 eV. The computed values of the FranckCondon integral and intensity are favorable for observing the (0,0) transition. High-level ab initio calculations at the CCSD(T) level of theory produce an estimated anharmonic frequency of 546 cm1 for HCO3 and a value of 3.79 eV for the (0,0) transition, both in good agreement with the experimentally determined values. SECTION: Dynamics, Clusters, Excited States
A
s one of the prominent species in the global carbon cycle, the bicarbonate anion (HCO3) is ubiquitously present in nature’s ecosystem. It plays a critical role in a broad variety of processes ranging from the pH homeostasis in oceans1 to the nucleation of noctilucent clouds,2 the calcification of external skeletons of organisms3 and the regulation of the mammalian blood pH.4 Bicarbonate is directly relevant to carbon capture and storage and a common anion in materials science. For these reasons, extensive studies, such as, in particular, vibrational spectroscopy, have been previously carried out in order to characterize HCO3 in solutions and crystalline forms.57 Valuable spectroscopic information has been obtained despite complications arising from the possible coexistence between HCO3 and CO32 in aqueous solutions and the presence of counterion interactions in solids. The benchmark nucleophilic reaction between OH and CO2 to form HCO3 was found to possess a substantial barrier in aqueous solutions,8,9 while no barrier is thought to exist in the gas phase.10,11 This distinct difference along the reaction coordinate in different environments has attracted many theoretical investigations, and the primary reasons were attributed to the different solvation environments between reactants and transition states.1215 Very recently, size-selected microhydrated bicarbonate clusters have been investigated in the gas phase via infrared (IR) action spectroscopy scanning the IR frequency range of the internal vibrational modes of HCO3.16 With the aid of accompanying r 2011 American Chemical Society
electronic structure calculations, a stepwise hydration motif between HCO3 and H2O has been proposed. To date, gas-phase studies of HCO3 have been surprisingly scarce. There is only one report about the thermochemical properties of isolated HCO3 anions studied via collision-induced dissociation and proton-transfer reactions in the gas phase.17 Many fundamental properties of the bare HCO3 species still remain unanswered. One notable example is the adiabatic electron detachment energy (ADE) of this anion, which is believed to be high due to its high stability, but to date, it has not been directly measured. The ADE of HCO3 was previously estimated from a thermodynamic cycle to be 3.4 eV using the gas-phase acidity of 339.4 kcal/mol for carbonic acid and the OH bond dissociation energy of 104 kcal/mol.17 However, the dissociative protonation threshold was later recalibrated by more than 9 kcal/mol to give rise to an EA value of 3.9895 eV that is currently listed in the NIST database.18 Considering the importance and ubiquity of HCO3, it is desirable to directly measure the ADE of this anion and to investigate the electronic structures and geometries of both the HCO3 anion and the neutral HCO3 radical. Gas-phase anion photoelectron spectroscopy (PES) has been previously shown to be a powerful experimental technique, not Received: March 10, 2011 Accepted: April 27, 2011 Published: April 29, 2011 1204
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The Journal of Physical Chemistry Letters only directly yielding ADEs of anions but also probing the ground and excited states of the corresponding neutral species.19 By coupling PES with an electrospray ionization source (ESI), many pristine anions found in the condensed phase can now easily be transported into the vacuum and have already been investigated in the gas phase.20,21 However, the (0,0) vibrational transitions in the threshold regions of the spectra are not often resolved, thus preventing the accurate determination of ADEs particularly for polyatomic anions with sizable, multicomponent geometric changes upon the removal of the additional electrons. Recent developments in the integration of cold ion trap techniques with PES have resulted in significant spectral sharpening in the threshold of the PES spectra due to the effective vibrational cooling and elimination of hot bands and often lead to vibrationally resolved features otherwise unattainable at room temperature.2123 In these cases, the ADEs can be measured precisely from the resolved (0,0) transitions. In this Letter, we report a low-temperature PES study of the gasphase HCO3 anion employing a recently developed cold and temperature-controlled ESI-PES apparatus24 at 266 (4.661 eV) and 193 nm (6.424 eV). A very broad weak feature in the low binding energy regime and a sharp intense peak at high binding energy are observed at 193 nm due to transitions from the ground state of the anion to ground and excited states of the neutral. The unresolved rising edge of the spectrum at 193 nm is partially resolved at 266 nm and T = 20 K, yielding an ADE of 3.680 ( 0.015 eV. High-level ab initio computations have been carried out to characterize the anion and neutral geometries and their electronic structures. The best computed ADE for the (0,0) transition that includes anharmonic zero-point energy corrections is 3.79 eV at the CCSD(T)/CBS (complete basis set) level of theory, a value that is just 0.11 eV larger than the experimental measurement. Experimental Approach: Low-Temperature ESI-PES. The lowtemperature ESI-PES apparatus has been described in detail before; a key feature of the apparatus is a temperature-controlled ion trap that is used for ion accumulation and cooling.24 The bicarbonate anions were produced by the electrospray of a 0.4 mM aqueous acetonitrilic solution of sodium bicarbonate salt. The produced anions were guided by two RF-only quadruples directed by a 90 ion bender to the temperature-controlled ion trap set at T = 20 K, where they were accumulated and cooled via collisions with a background gas of ∼0.1 mTorr of 20% H2 balanced in helium. The ions were trapped and cooled for a period of 2080 ms before being pulsed out into the extraction zone of a time-of-flight mass spectrometer with a repetition rate of 10 Hz. During the PES experiment, the HCO3 anions were massselected and decelerated before being intercepted by a probe laser beam in the photodetachment zone of the magnetic bottle photoelectron analyzer. In the current experiment, two photon energies at 266 nm (4.661 eV) from a Nd:YAG laser and 193 nm (6.424 eV) from an ArF excimer laser were used. The laser was operated at a 20 Hz repetition rate with the ion beam off at alternating laser shots for shot-by-shot background subtraction. Photoelectrons were collected at nearly 100% efficiency by a magnetic bottle and analyzed in a 5.2 m long electron flight tube. Time-of-flight photoelectron spectra were collected and converted to kinetic energy spectra, calibrated by the known spectra of I and ClO2. The electron binding energy spectra were obtained by subtracting the kinetic energy spectra from the detachment photon energies. The energy resolution (ΔE/E) was about 2%, that is, ∼20 meV for 1 eV electrons.
LETTER
Figure 1. The geometries of HCO3/HCO3 with the definition of the bond lengths and angles and the labeling of the atoms.
Theoretical Approach. First-principles electronic structure calculations were used to calculate the ADE of HCO3. These were carried out at the HartreeFock [unrestricted HF (UHF) for HCO3], second-order MøllerPlesset perturbation theory (MP2), and coupled cluster expansion including singles, doubles, and a perturbative estimate of triples replacements [CCSD(T)] levels of theory using the family of augmented correlationconsistent basis sets, aug-cc-pVnZ (n = D, T, Q), of Dunning and co-workers.25,26 For each level of theory, the geometries were optimized with the aug-cc-pVDZ and aug-cc-pVTZ basis sets, and the latter were used for single-point energy calculations with the largest aug-cc-pVQZ basis set used in this study. The ADE was calculated as the energy difference between the global minima of HCO3 (1A0 state) and HCO3 (2A0 state) (cf. Figure 1), evaluated at each level of theory and basis set. All MP2 geometry optimizations and subsequent calculations of FranckCondon intensities for vibronic transitions between the anion and neutral potential energy surfaces were performed with the Gaussian 03 suite of codes,27 whereas all CCSD(T) calculations were carried out with the NWChem suite of electronic structure codes.28 All open-shell coupled cluster calculations for HCO3 were based on a doublet restricted open-shell Hartree Fock (ROHF) reference with the core electrons being frozen. These calculations were performed using the tuned tensor contraction engine (TCE)29 implementation of the CCSD30 and CCSD(T)31 approaches (for details and scalability analysis, see ref 32) implemented within the NWChem suite of electronic structure codes.28 Anharmonic frequencies and zero-point energies were estimated from second-order vibrational perturbation theory (VPT2; see refs 3335) as implemented in the Gaussian 03 suite of codes.27 Low-Temperature PES Spectra. Figure 2 shows the T = 20 K PES spectra of HCO3 at (a) 266 and (b) 193 nm. The 193 nm spectrum exhibits a very broad feature with some discernible features spanning from 3.6 to 4.9 eV (X), followed by a sharp and intense peak starting at 5.11 eV with a partially resolved vibrational progression of 560 ( 40 cm1 (A). The rather weak and slowly rising edge of X is better-resolved and amplified at 266 nm, showing a partially resolved structure dominant with one vibrational mode of 530 ( 20 cm1. The tiny wiggle line from 3.3 to 3.6 eV in the 266 nm spectra is in fact due to the imperfection of the background subtraction, as evidenced from the fact that some part of the line goes below the baseline. The computed FranckCondon integral for the (0,0) transition has a value of 0.25 101 and an intensity of 0.34 102. These values are half of the largest one (for the integral) and an order of 1205
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LETTER
magnitude larger (for the intensity) among all single overtone Æn|mæ integrals, where n = initial state and m = final state. This information suggests that conditions are favorable for observing the (0,0) transition, and we therefore determine the ADE of HCO3 or the electron affinity (EA) of the HCO3 radical from the first resolved peak to be 3.680 ( 0.015 eV. Note that our instrument resolution of about 250 cm1 at 266 nm for the electrons in the X range would have resulted in a much better resolved spectrum if only the one vibrational mode of 530 cm1 was involved. The fact that the rising edge of X is broad and only partially resolved indicates that the electron detachment induces excitations of multiple vibrational modes and results in a rather complex spectral feature. This is consistent with the computed changes in the optimized geometries of HCO3 and HCO3 (see Table 1 below), for which bond lengths and angles change upon removal of the electron (largest changes: the R3(CO(H)) bond is shortened by 0.11 Å, and the
Figure 2. Low-temperature (T = 20 K) photoelectron spectra of HCO3 at (a) 266 (4.661 eV) and (b) 193 nm (6.424 eV).
a2(OCO(H)) angle is increased by 12.7). On the other hand, the (0,0) transition was observed in our previous study of the photodetachment of CH3CO2, where there was a 19 decrease in the OCO angle,23 suggesting that the FranckCondon factor can be favorable for observing the (0,0) transition for this range of angle changes. Our assignment of the first resolved peak of the spectra to the (0,0) transition is therefore supported by the calculation of the FranckCondon factors and the good agreement between the calculated (vide infra) and measured ADEs. Structures and Vibrational Frequencies of HCO3 and HCO3. The optimal geometrical parameters (bond lengths and bond angles; cf. Figure 1) for the anion and the radical at the various levels of theory are listed in Table 1. As a general trend, the correlated methods produce longer bond lengths (by 0.020.03 Å) with respect to HF, whereas the effect of the larger aug-ccpVTZ basis set is to slightly contract them (by ∼0.01 Å) with respect to the smaller aug-cc-pVDZ basis set. The harmonic frequencies of HCO3 and HCO3 at the MP2 and CCSD(T) levels of theory with the aug-cc-pVTZ basis set, together with a brief description of the corresponding normal modes, are listed in Table 2. The anharmonicities (anharm.) in the same table are estimated at the MP2/aug-cc-pVDZ level of theory via VPT2. No scaling factors were used for the vibrational frequencies. It should be noted that IR frequencies for clusters of the hydrated anion as well as many solution-phase IR absorption spectra have been reported, but to date, the gas-phase IR spectra for the isolated HCO3 anion have not been measured. For the anion (HCO3), the out-of-plane OH motion (A00 symmetry) is the lowest-frequency mode. At the MP2/aug-ccpVTZ level, the harmonic frequency is slightly higher (by just 1 cm1) than the one corresponding to the OH in-plane rocking vibration (A0 symmetry). However, the anharmonicity of the first mode (29 cm1) is almost three times larger than the one for the second (10 cm1), and this produces an anharmonic frequency of 519 cm1 for the out-of-plane mode compared to 537 cm1 for the in-plane one at the MP2 level. The CCSD(T)/aug-cc-pVTZ harmonic frequencies agree with this order. Given the fact that the anharmonicities are probably converged at the MP2 level, our best estimates for the anharmonic frequencies of the two modes (obtained by adding the MP2/aug-cc-pVDZ anharmonicities to the
Table 1. Optimal Geometries of HCO3 and HCO3 at Various Levels of Theory and Basis Setsa level of theory
basis set
R1(CO) Å
R2(CO) Å
R3(CO) Å
r(OH) Å
a1 deg.
a2 deg.
a3 deg.
HCO3 (1A0 ) HF
aug-cc-pVDZ
1.2217
1.2367
1.3977
0.9425
131.44
113.99
104.43
MP2
aug-cc-pVTZ aug-cc-pVDZ
1.2158 1.2490
1.2308 1.2649
1.3938 1.4589
0.9398 0.9692
131.41 132.74
113.98 113.57
104.64 101.10
aug-cc-pVTZ
1.2386
1.2549
1.4442
0.9649
132.59
113.48
100.90
aug-cc-pVDZ
1.2498
1.2661
1.4543
0.9689
132.53
113.61
101.48
aug-cc-pVTZ
1.2387
1.2552
1.4386
0.9642
132.35
113.53
101.32
CCSD(T)
HCO3 (2A0 ) HF
a
aug-cc-pVDZ
1.1729
1.3353
1.3191
0.9475
122.45
111.87
112.73
aug-cc-pVTZ
1.1672
1.3305
1.3141
0.9449
122.51
111.78
113.19
MP2
aug-cc-pVDZ
1.2068
1.3483
1.3524
0.9730
121.84
112.64
110.05
CCSD(T)
aug-cc-pVTZ aug-cc-pVDZ
1.1967 1.2723
1.3365 1.2566
1.3409 1.3396
0.9688 0.9738
121.85 114.92
112.56 125.34
110.28 107.57
aug-cc-pVTZ
1.2735
1.2347
1.3278
0.9690
115.44
126.27
107.46
The definition of the bond lengths and angles is from Figure 1. 1206
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Table 2. Harmonic Frequencies (cm1) and IR Intensities (km/mol) of HCO3 and HCO3 Obtained with the aug-cc-pVTZ Basis Seta MP2 mode
sym.
description
harmonic cm
1
CCSD(T)
intensity km/mol anharm. cm1 harmonic cm1
HCO3 (1A0 ) 00
ν1
A
OH out-of-plane
548
76
29
517
ν2 ν3
A0 A0
OH in-plane rocking CO(H) stretch þ scissor OCO bend out-of-phase
547 629
11 5
10 14
552 633
ν4
A00
OCO out-of-plane wag
820
18
12
826
ν5
A0
CO(H) stretch þ scissor OCO bend in-phase
849
251
35
871
ν6
A0
COH bend
1191
92
41
1209
ν7
A0
OCO symmetric stretch
1293
364
32
1303
ν8
A0
OCO asymmetric stretch
1763
794
28
1755
ν9
A0
OH stretch
3807
17
190
3803
ZPE, harmonic (kcal/mol) ZPE, anharmonic (kcal/mol)
16.36 16.17
16.40 (16.21)
HCO3 (2A0 ) 0
ν1
A
OCO(H) bending (H outside)
424
28
10
422
ν2
A00
OH out-of-plane
385
118
22
474
ν3
A0
OCO(H) bending (H inside)
571
3
7
553
ν4
A00
OCO out-of-plane wag
765
19
16
748
ν5
A0
OCO(H) symmetric stretch
950
42
19
965
ν6
A0
OCO asymmetric stretch
1164
26
20
1145
ν7 ν8
A0 A0
COH Bend CO(H) stretch
1344 1826
359 302
47 33
1265 1600
ν9
A0
OH stretch
3768
94
195
3765
ZPE, harmonic (kcal/mol) ZPE, anharmonic (kcal/mol)
a
16.01
15.64
(15.81)
(15.44)
Δ(ZPE), harmonic (kcal/mol)
0.35
0.76
Δ(ZPE), anharmonic (kcal/mol)
0.36
0.77
Anharmonicities (anharm.) are estimated at the MP2/aug-cc-pVDZ level.
CCSD(T)/aug-cc-pVTZ harmonic frequencies) are 488 (A 00 ) and 542 cm1 (A0 ). For the HCO3 radical, MP2 predicts the out-of-plane OH vibration (A00 ) to be the lowest one; however, this is not the case at the CCSD(T) level, which gives the mode corresponding to the in-plane OH rocking vibration (A0 ) to be the lowest one. According to our results, the experimentally resolved frequency of 530 ( 20 cm1 for this species corresponds to a higher-lying mode of A0 symmetry representing the OCO(H) bending (H inside). The anharmonic MP2 frequency for that mode is 564 cm1. By adding the MP2/aug-cc-pVDZ anharmonicity of 7 cm1 for that mode (cf. Table 2) to the CCSD(T)/aug-ccpVTZ harmonic frequency, we obtain a best estimate of 546 cm1, which is within the upper limit of the experimentally resolved frequency. The significant bond angle increase of a2 (from 113.5 to 126.3 in Table 1) upon removal of the additional electron is consistent with the excitation of the OCO(H) bending (H inside) mode and the long vibrational progression observed in the spectrum (see also the Abstract graphic). Table 2 also lists the energy difference in the zero-point energies between the anion and the radical. It is interesting to note that the harmonic energy differences are identical to the ones including anharmonic effects estimated via VPT2. However, the zero-point energy difference between the anion and the
radical at the CCSD(T) level is 0.4 kcal/mol larger than the corresponding one at the MP2 level, reflecting the difference in the harmonic frequencies obtained with the two levels of theory. This estimated zero-point energy difference between the two species will be used in our subsequent estimation of the (0,0) ADE in order to compare to the one measured experimentally. Calculated ADEs. The energies of the optimized geometries of HCO3 and HCO3 are listed in Table 3 together with the ADEs that correspond to the differences between the two potential wells. We note that electron correlation plays a significant role in the accurate estimate of the ADE. At the HF level, the ADE is underestimated by ∼1.5 eV when compared to experiment. On the other hand, MP2 was found to overestimate by ∼0.8 eV, as was the case for the VDEs of the CN(H2O)n clusters reported earlier.36,37 In contrast, the ADE obtained at the CCSD(T) level is very close to the experimentally obtained value. The [T] results listed in Table 3 include only the fourth-order terms due to triples. The CCSD(T) results include fourth- and fifth-order contributions due to triples. The fifth-order contribution helps to balance the correlation effects in the vicinity of the equilibrium geometries.38 The estimated CBS limits for the ADE are 3.65 eV for CCSD[T] and 3.82 eV for CCSD(T), extrapolated from the results with the aug-cc-pVnZ sets (n = D, T, Q) using a 1207
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Table 3. Energies of Optimized Structures for the Anion (HCO3) and Neutral Species (HCO3) and the Resulting Adiabatic Detachment Energy (ADE) at Various Levels of Theory and Basis Sets level of theory HF/UHF
MP2/UMP2
CCSD
CCSD[T]
basis set
anion au
neutral au
aug-cc-pVDZ
263.14224754
263.05565221
2.36
aug-cc-pVTZ aug-cc-pVQZ
263.20552796 263.22285282
263.12083497 263.13850567
2.30 2.30
aug-cc-pVDZ
263.87535080
263.72085872
4.20
aug-cc-pVTZ
264.09523324
263.93632896
4.32
aug-cc-pVQZ
264.17033093
264.00768222
4.42
aug-cc-pVDZ
263.87662302
263.73999033
3.72
aug-cc-pVTZ
264.08722197
263.95093158
3.71
aug-cc-pVQZ
264.15454350
264.01641284
3.76
aug-cc-pVDZ aug-cc-pVTZ
263.9076576 264.1300921
263.7891838 263.9988586
3.22 3.57
aug-cc-pVQZ
264.2002546
264.0669363
est. CBS limit CCSD(T)
ADE eV
3.63 3.65
aug-cc-pVDZ
263.90486448
263.77201822
3.61
aug-cc-pVTZ
264.12762179
263.99094074
3.72
aug-cc-pVQZ
264.19787602
264.05920073
est. CBS limit
3.77 3.82
best computed energy difference best estimated energy difference
3.77 3.82
best estimate for (0,0) transition
3.79
exp. for (0,0) transition
3.680 ( 0.015
(45) polynomial3945 (a three-point exponential extrapolation39,4345 produces results that are within 0.01 eV of those limits). It should be noted that this heuristic extrapolation results in a CBS limit that is just 0.05 eV away (larger) from the best computed CCSD(T)/aug-cc-pVQZ ADE of 3.77 eV. By incorporating the difference of 0.77 kcal/mol (0.03 eV) between the anion and the radical anharmonic zero-point energies (discussed in the previous section), we arrive at a best estimate of 3.79 eV for the (0,0) transition, which is just 0.11 eV larger than the experimentally obtained result. The observed peak at 5.11 eV in the 193 nm spectra (cf. Figure 2b) corresponds to an excited state of the neutral radical. The first excited state of 2A00 symmetry for the neutral arises from a single excitation from the ground state’s doubly occupied O3(pz) (a00 symmetry) orbital to the singly occupied O4(pxpy) (a0 symmetry) orbital (the molecule lies in the xy plane; see Figure 1 for the labeling of the atoms). At the CCSD/aug-ccpVQZ level of theory, the first excited state of 2A00 symmetry is computed to be 0.75 eV above the neutral ground state, that is, at an absolute energy of 4.51 eV (note that the ADE at this level of theory/basis set is 3.76 eV from Table 3). This value agrees well with the second group feature within the X band (Figure 2), indicating that the X band actually has contributions from both the ground and the first excited states of HCO3. In contrast, the first excited state of 2A0 symmetry lies 2.3 eV above the neutral ground state, a range that is close or above the accessible energy range of our experiment (6.4 eV). Here, we make the tentative assignment that feature A is due to the transition from the ground state of the anion to the second excited state of the neutral with 2 00 A symmetry. In conclusion, a joint experimentaltheoretical study was carried out to measure and analyze the first direct photoelectron photodetachment of HCO3 in the gas phase under lowtemperature conditions. We have partially resolved a single
vibrational progression with a frequency of 530 ( 20 cm1 in the threshold of the 266 nm spectrum obtained at T = 20 K. We determined this frequency to correspond to the OCO(H) bending mode of the HCO3 radical at 546 cm1 at the CCSD(T)/aug-cc-pVTZ level of theory including anharmonic corrections. The adiabatic electron detachment energy (ADE) of HCO3 was experimentally determined from the (0,0) transition to be 3.680 ( 0.015 eV. The calculated FranckCondon factors confirm that the observation of this transition is favorable. The best estimated, at the CCSD(T)/CBS level of theory, (0,0) transition that includes anharmonic corrections for the potential wells of the anion and the radical is 3.79 eV, just 0.11 eV away from the experimentally measured value.
’ AUTHOR INFORMATION Corresponding Author
*E-mail:
[email protected] (X.-B.W.); sotiris.xantheas@pnl. gov. (S.S.X.).
’ ACKNOWLEDGMENT This work was supported by the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences, U.S. Department of Energy (DOE). Part of this work was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory, which is operated by Battelle for the DOE. This research was performed in part using the Molecular Science Computing Facility (MSCF) in the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research. 1208
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The Journal of Physical Chemistry Letters Additional computer resources were provided by the Office of Basic Energy Sciences, U.S. Department of Energy at the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science user facility at Lawrence Berkeley National Laboratory.
’ REFERENCES (1) Caldeira, K.; Wickett, M. E. Anthropogenic Carbon and Ocean pH. Nature 2003, 425, 365. (2) Plane, J. M. C. The Role of Sodium Bicarbonate in the Nucleation of Noctilucent Clouds. Ann. Geophys. 2000, 18, 807–814. (3) Orr, J. C.; Fabry, V. J.; Aumont, O.; Bopp, L.; Doney, S. C.; Feely, R. A.; Gnanadesikan, A.; Gruber, N.; Ishida, A.; Joos, F.;Anthropogenic Ocean Acidification over the Twenty-First Century and Its Impact on Calcifying Organisms. Nature 2005, 437, 681–686. (4) Silverman, D. N.; Lindskog, S. The Catalytic Mechanism of Carbonic Anhydrase: Implications of a Rate-Limiting Protolysis of Water. Acc. Chem. Res. 1988, 21, 30–36. (5) Rudolph, W. W.; Irmer, G.; K€onigsberger, E. Speciation Studies in Aqueous HCO3CO32 Solutions. A Combined Raman Spectroscopic and Thermodynamic Study. Dalton Trans. 2008, 900–908. (6) Rudolph, W. W.; Fischer, D.; Irmer, G. Vibrational Spectroscopic Studies and Density Functional Theory Calculations of Speciation in the CO2Water System. Appl. Spectrosc. 2006, 60, 130–144. (7) Dobson, K. D.; McQuillan, A. J. An Infrared Spectroscopic Study of Carbonate Adsorption to Zirconium Dioxide SolGel Films from Aqueous Solutions. Langmuir 1997, 13, 3392–3396. (8) Pinsent, B. R. W.; Pearson, L.; Roughton, F. J. W. The Kinetics of Combination of Carbon Dioxide with Hydroxide Ions. Trans. Faraday Soc. 1956, 52, 1512–1520. (9) Palmer, D. A.; van Eldik, R. The Chemistry of Metal Carbonato and Carbon Dioxide Complexes. Chem. Rev. 1983, 83, 651–731. (10) J€onsson, B.; Karlstr€om, G.; Wennerstr€om, H. Ab Initio Molecular Orbital Calculations on the WaterCarbon Dioxide System. The Reaction OH þ CO2 f HCO3. J. Am. Chem. Soc. 1978, 100, 1658–1661. (11) Liang, J. Y.; Lipscomb, W. N. Theoretical Study of the Uncatalyzed Hydration of Carbon Dioxide in the Gas Phase. J. Am. Chem. Soc. 1986, 108, 5051–5058. (12) Leung, K.; Nielsen, I. M. B.; Kurtz, I. Ab Initio Molecular Dynamics Study of Carbon Dioxide and Bicarbonate Hydration and the Nucleophilic Attack of Hydroxide on CO2. J. Phys. Chem. B 2007, 111, 4453–4459. (13) Iida, K.; Yokogawa, D.; Sato, H.; Sakaki, S. The Barrier Origin on the Reaction of CO2 þ OH in Aqueous Solution. Chem. Phys. Lett. 2007, 443, 264–268. (14) Nemukhin, A. V.; Topol, I. A.; Grigorenko, B. L.; Burt, S. K. On the Origin of Potential Barrier for the Reaction OH þ CO2 f HCO3 in Water: Studies by Using Continuum and Cluster Solvation Methods. J. Phys. Chem. B 2002, 106, 1734–1740. (15) Peng, Z.; Merz, K. M., Jr. Theoretical Investigation of the OH þ CO2 f HCO3 Reaction in the Gas and Aqueous Phases. J. Am. Chem. Soc. 1993, 115, 9640–9647. (16) Garand, E.; Wende, T.; Goebbert, D. J.; Bergmann, R.; Meijer, G.; Neumark, D. M.; Asmis., K. R. Infrared Spectroscopy of Hydrated Bicarbonate Anion Clusters: HCO3(H2O)110. J. Am. Chem. Soc. 2010, 132, 849–856. (17) Squires, R. R. Gas-Phase Thermochemical Properties of the Bicarbonate and Bisulfite Ions. Int. J. Mass. Spectrom. Ion Processes 1992, 117, 565–600. (18) NIST Chemistry Webbook. http://webbook.nist.gov (Nov. 2010). (19) Rienstra-Kiracofe, J. C.; Tschumper, G. S.; Schaefer, H. F., III; Nandi, S.; Ellison, G. B. Atomic and Molecular Electron Affinities: Photoelectron Experiments and Theoretical Computations. Chem. Rev. 2002, 102, 231–282.
LETTER
(20) Wang, X. B.; Yang, X.; Wang, L. S. Probing Solution Phase Species and Chemistry in the Gas Phase. Int. Rev. Phys. Chem. 2002, 21, 473–498. (21) Wang, X. B.; Wang, L. S. Photoelectron Spectroscopy of Multiply Charged Anions. Annu. Rev. Phys. Chem. 2009, 60, 105–126. (22) Wang, X. B.; Fu, Q.; Yang, J. Electron Affinities and Electronic Structures of o-, m-, and p-Hydroxyphenoxyl Radicals: A Combined Low-Temperature Photoelectron Spectroscopic and Ab Initio Calculation Study. J. Phys. Chem. A 2010, 114, 9083–9089. (23) Wang, X. B.; Woo, H. K.; Wang, L. S.; Minodar, B.; Jungwirth, P. Determination of the Electron Affinity of the Acetyloxyl Radical (CH3COO) by Low-Temperature Anion Photoelectron Spectroscopy and ab Initio Calculations. J. Phys. Chem. A 2006, 110, 5047–5050. (24) Wang, X. B.; Wang, L. S. Development of a Low-Temperature Photoelectron Spectroscopy Instrument Using an Electrospray Ion Source and a Cryogenically Controlled Ion Trap. Rev. Sci. Instrum. 2008, 79, 073108/1–073108/8. (25) Dunning, T. H., Jr. Gaussian Basis Sets for Use in Correlated Molecular Calculations. I. The Atoms Boron through Neon and Hydrogen. J. Chem. Phys. 1992, 90, 1007–1023. (26) Kendall, R. A.; Dunning, T. H., Jr.; Harrison, R. J. Electron Affinities of the First-Row Atoms Revisited. Systematic Basis Sets and Wave Functions. J. Chem. Phys. 1992, 96, 6796–6806. (27) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K. N.; Burant, J. C., Gaussian 03, Revision E.01, Gaussian, Inc.: Wallingford, CT, 2004. (28) (a) Kendall, R. A.; Apra, E.; Bernholdt, D. E.; Bylaska, E. J.; Dupuis, M.; Fann, G. I.; Harrison, R. J.; Ju., J.; Nichols, J. A.; Nieplocha, J.; Straatsma, T. P.; Windus, T. L.; Wong, A. T. High Performance Computational Chemistry: An Overview of NWChem a Distributed Parallel Application. Comput. Phys. Commun. 2000, 128, 260–283.(b) High Performance Computational Chemistry Group NWChem, A Computational Chemistry Package for Parallel Computers, version 4.6; Pacific Northwest National Laboratory: Richland, WA, 2003. (29) Hirata, S. Tensor Contraction Engine: Abstraction and Automated Parallel Implementation of Configuration-Interaction, CoupledCluster, and Many-Body Perturbation Theories. J. Phys. Chem. A 2003, 107, 9887–9897. (30) Purvis, G. D., III; Bartlett, R. J. A Full Coupled-Cluster Singles and Doubles Model: The Inclusion of Disconnected Triples. J. Chem. Phys. 1982, 76, 1910–1918. (31) Raghavachari, K.; Trucks, G. W.; Pople, J. A.; Head-Gordon, M. A Fifth-Order Perturbation Comparison of Electron Correlation Theories. Chem. Phys. Lett. 1989, 157, 479–483. (32) Fan, P. D.; Valiev, M.; Kowalski, K. Large-Scale Parallel Calculations with Combined Coupled Cluster and Molecular Mechanics Formalism: Excitation Energies of Zinc-Porphyrin in Aqueous Solution. Chem. Phys. Lett. 2008, 458, 205–209. (33) Barone, V. Characterization of the Potential Energy Surface of the HO2 Molecular System by a Density Functional Approach. J. Chem. Phys. 1994, 101, 10666–10676. (34) Barone, V.; Adamo, C.; Minichino, C. Direct Catalytic Effect and Fine Modulation of Solvent in the Keto-Enol Isomerization of Amides. J. Mol. Struct.: THEOCHEM 1995, 330, 325–333. (35) Minichino, C.; Barone, V. From Concepts to Algorithms for the Characterization of Reaction Mechanisms. H2CS as a Case Study. J. Chem. Phys. 1994, 100, 3717–3741. (36) Wang, X. B.; Werhahn, J.; Wang, L. S.; Kowalski, K.; Laubereau, A.; Xantheas, S. S. Observation of a Remarkable Temperature Effect in the Hydrogen Bonding Structure and Dynamics of the CN(H2O) Cluster. J. Phys. Chem. A 2009, 113, 9579–9584. (37) Wang, X. B.; Kowalski, K.; Wang, L. S.; Xantheas, S. S. Stepwise Hydration of the Cyanide Anion: A Temperature-Controlled Photoelectron Spectroscopy and Ab-Initio Computational Study of CN(H2O)n (n = 25). J. Chem. Phys. 2010, 132, 124306. (38) Urban, M.; Noga, J.; Cole, S. J.; Bartlett, R. J. Towards a full CCSDT model for electron correlation. J. Chem. Phys. 1985, 83, 4041. 1209
dx.doi.org/10.1021/jz200327f |J. Phys. Chem. Lett. 2011, 2, 1204–1210
The Journal of Physical Chemistry Letters
LETTER
(39) Xantheas, S. S. On the Importance of the Fragment Relaxation Energy Terms in the Estimation of the Basis Set Superposition Error (BSSE) Correction to the Intermolecular Interaction Energy. Letter to the Editor. J. Chem. Phys. 1996, 104, 8821–8824. (40) Klopper, W. Limiting Values for MøllerPlesset Second-Order Correlation Energies of Polyatomic Systems: A Benchmark Study on Ne, HF, H2O, N2, and He 3 3 3 He. J. Chem. Phys. 1995, 102, 6168–6179. (41) Bunge, C. F. Electronic Wave Functions for Atoms. II. Some Aspects of the Convergence of the Configuration Interaction Expansion for the Ground States of the He Isoelectronic Series. Theor. Chim. Acta 1970, 16, 126–144. (42) Termath, V.; Klopper, W.; Kutzelnigg, W. Wave Functions with Terms Linear in the Interelectronic Coordinates to Take Care of the Correlation Cusp. II. Second-Order MøllerPlesset (MP2-R12) Calculations on Closed-Shell Atoms. J. Chem. Phys. 1991, 94, 2002–2019. (43) Xantheas, S. S.; Dunning, T. H., Jr. Theoretical Estimate of the Enthalpy of Formation of HSO and HSOSOH Isonerization Energy. J. Phys. Chem. 1993, 97, 18–19. (44) Xantheas, S. S.; Dunning, T. H., Jr. Theoretical Studies of Sulfurous Species of Importance in Atmospheric Chemistry. 1. Characterization of the HSO and SOH Isomers. J. Phys. Chem. 1993, 97, 6616–6627. (45) Peterson, K. A.; Kendall, R. A.; Dunning, T. H., Jr. Benchmark Calculations with Correlated Molecular Wave Functions. II. Configuration Interaction Calculations on First Row Diatomic Hydrides. J. Chem. Phys. 1993, 99, 1930–1944.
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