Collision Induced Complex Formation following Electron Capture of

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Collision Induced Complex Formation following Electron Capture of SO2 H2O Complex Interacting with Argon Atoms Hiroto Tachikawa* Division of Materials Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan

bS Supporting Information ABSTRACT: Electron capture dynamics of SO2 H2O(Ar)n complexes (n = 0 2) have been investigated by means of direct ab initio molecular dynamics (MD) method in order to elucidate the effects of solvent argon on the reaction dynamics of SO2 H2O. The neutral complex of SO2 H2O has a Cs symmetry, and the sulfur of SO2 interacts with the oxygen of H2O with an eclipsed form. In the SO2 H2O(Ar)n complexes, the dipole of H2O interacts with the argon atoms in the most stable structure. Following the electron capture of the complex SO2 H2O, the complex anion SO2 (H2O) is dissociated directly into SO2 + H2O. On the other hand, the electron capture of SO2(H2O)(Ar)n argon complex (n = 1 2) leads to the anion water complex SO2 (H2O) because the collision of H2O with the Ar atom causes a rebound of H2O from Ar atom to the SO2 anion. The argon solvent enhanced the SO2 (H2O) complex formation. The reaction mechanism of SO2(H2O) in the participation of argon atoms was discussed on the basis of the present results.

1. INTRODUCTION Chemistry of sulfur dioxide (SO2) consists of wide fields from basic science to technological application. The SO2 molecule is an air pollutant formed as one byproduct of fossil fuel combustion as well as nitrogen dioxide (NO2). SO2 easily forms a complex with water molecules in gas phase and in the atmosphere. The hydrated complex SO2(H2O)n becomes a source of sulfuric acid and a major constituent of acid rain.1 3 Therefore, several investigations on the interaction of SO2 with water molecules have been performed for a long time. To elucidate the electronic properties of SO2(H2O)n, many of experiments and theoretical works have been carried out.4 6 From vibrational sum-frequency spectroscopy (VSFS), Tarbuck and Richmond5,6 showed that the SO2 on water ice surface interacts with a water molecule. The sulfur atom of SO2 binds to the oxygen atom of H2O on a surface and a 1:1 complex is formed. In the case of SO2 in polar stratospheric clouds (PSCs), cosmic rays cause ionization of water ice constituting PSCs and the electron attacks SO2 adsorbed on ice. The complex SO2(H2O)n will capture an excess electron. Robertson et al. measured mid-IR argon predissociation spectra of SO2 (H2O)(Ar)n (n = 1 3). They showed that the complex anion has a symmetrical structure where the oxygen atoms of SO2 bind to hydrogen atoms of H2O.7 They also found that SO2 (H2O) is always surrounded by “argon solvent” as SO2 (H2O)(Ar)n (n = 1 3). Woronowicz et al. calculated the structure of SO2 (H2O) complex anion and showed that the hydrogen atoms of H2O bind to the oxygen atoms of SO2 .8 The two hydrogen atoms are equivalent to each other. Namely, each hydrogen atom of H2O r 2011 American Chemical Society

interacts with each oxygen atom of SO2 , and the complex has a C2v symmetry. This result supports to the structure obtained by Robertson’s experiment.7 Thus, information on the static properties of SO2(H2O) and SO2 (H2O) has been accumulated. However, the electron capture dynamics of SO2(H2O) is scarcely known. In the present study, the electron capture dynamics of SO2 H2O complex have been investigated by means of a direct ab initio molecular dynamics (MD) method. In particular, we focus our attention on the effects of argon solvent on the electron capture dynamics of SO2(H2O). Time scales of hydrogen bond breaking and re-formation processes between SO2 and H2O were mainly investigated.

2. METHOD OF CALCULATION First, we calculated the structures of SO2(H2O) and SO2(H2O)(Ar)n (n = 1 2) and its anionic systems at the second-order Møller Plesset perturbation (MP2), coupled cluster with single and double excitations (CCSD), and quadratic configuration interaction with single and double excitations (QCISD) methods with the 6-311++G(d,p) basis set. In order to check basis set dependency on the structures, aug-cc-pVDZ and aug-cc-pVTZ were also used in the SO2(H2O) system (see Supporting Information). The restricted and unrestricted Hartree Fock orbitals were used for neutral and anionic systems, respectively. We use the usual convention of the computational methods, MP2 and Received: March 24, 2011 Revised: July 4, 2011 Published: July 17, 2011 9091

dx.doi.org/10.1021/jp202778t | J. Phys. Chem. A 2011, 115, 9091–9096

The Journal of Physical Chemistry A

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Figure 1. Optimized structures of SO2(H2O) neutral complex and anionic complex calculated at the QCISD/6-311++G(d,p) level. Neutral and anion complexes have Cs and C2v symmetries, respectively. Anion complex is a planar structure.

UMP2, for the closed- and open-shell systems, respectively, from now. The usual frozen core approximation was employed for both anionic and neutral states. All static ab initio calculations were carried out using Gaussian 03 and Gaussian 09 programs.9,10 In direct ab initio molecular dynamics (MD) calculations,11 14 the potential energy and its gradient were calculated at the UMP2/ 6-311++G(d,p) level for anionic systems and used without the basis set superposition error (BSSE) corrections in the trajectory calculations. The equation of motion was solved by the velocity Verlet algorithm with a time step of 0.25 fs. The drifts of total energies were less than 1.0 10 4% in all steps in all of the trajectory calculations. No symmetry restrictions were applied to the calculation of the energy gradients. The calculated values of ÆS2æ were less than 0.77 at all trajectory points. The structures of SO2(H2O) used in the direct ab initio MD calculations were selected as follows. First, the geometries around the equilibrium structure were randomly generated. Second, the energy difference between each generated geometry and the equilibrium structure was calculated. Ten geometries possessing energy difference lower than 2.0 kcal/mol were selected. In the case of SO2(H2O)(Ar)n (n = 1 2), the optimized structures were used. The initial internal vibrational energy of the complex was assumed to zero. The electron collision energy was completely neglected in the present study.

3. RESULTS A. Structures of SO2 H2O and (SO2 H2O) Complexes. The optimized structure of SO2 H2O complex is illustrated in Figure 1. The sulfur atom of SO2 is bound to the oxygen atom of H2O. The intermolecular sulfur oxygen distance is calculated to be R1 = 2.839 Å at the QCISD/6-311++G(d,p) level. The structures of SO2 and H2O were hardly changed by the complex formation; for example, the S O distances of SO2 and SO2(H2O) are 1.450 and 1.451 Å, respectively. The O H

Figure 2. Snapshots of SO2 (H2O) following electron attachment of neutral complex 1:1 complex. Direct ab initio MD calculation was carried out at the MP2/6-311++G(d,p) level. Values indicate intermolecular distance between SO2 and H2O as r(O S) distance (in angstroms). Arrows schematically indicate displacement direction.

distances of H2O and SO2(H2O) are 0.958 and 0.959 Å, respectively. The complex has a Cs symmetry. The binding energy of SO2 to H2O was calculated to be 5.5 kcal/mol (QCISD). The MP2 binding energy is 5.0 kcal/mol, which is in good agreement with that of QCISD value. To obtain the stable structure of anion complex, [SO2(H2O)] , several structures were examined as initial geometries in the optimization. However, only one structure was found as a stable form. The structure obtained is illustrated in Figure 1 (lower). Two oxygen atoms of SO2 anion orient to two oxygen atoms of H2O. The anion complex has a C2v structure and a planar structure. The interatomic distances, R1 and R4, are 3.477 and 2.061 Å, respectively. These values are in good agreement with previous theoretical calculations (the intermolecular O O distance is R4 = 2.017 vs 2.061 Å).7,8 B. Electron Attachment to the SO2 H2O Complex. Snapshots of anion water complex following the electron capture, [SO2(H2O)] , are illustrated in Figure 2. This trajectory was started from the optimized structure obtained by the MP2 level. The molecular charges on SO2 and H2O in the complex anion of SO2(H2O) are calculated to be 0.97 and 0.03, respectively, at time zero. This result indicates that the excess electron is localized on the SO2 moiety of the complex (time zero and point a) when the excess electron is vertically injected into the 9092

dx.doi.org/10.1021/jp202778t |J. Phys. Chem. A 2011, 115, 9091–9096


Figure 3. Result of direct ab initio MD calculation for electron capture of SO2(H2O) 1:1 complex: (A) intermolecular distance; (B) potential energy of the system. The corresponding snapshots are illustrated in Figure 2.

neutral complex. Hence, [SO2(H2O)] is schematically expressed as SO2 (H2O). The distance between SO2 and H2O is 2.875 Å as a sulfur oxygen distance (R1), and angles of O S O (θ) are close to 120 at time zero. After the electron capture of the complex, the water molecule rotates rapidly itself and the SO2 anion rotates slowly. The rotation of H2O is caused by reorientation of dipole moment of H2O toward SO2 , because a charge of SO2 moiety is suddenly changed from zero to 1 by electron capture. At time = 41 fs (point b), the intermolecular distance is 3.278 Å, which is 0.40 Å longer than that at time zero. This change indicates that H2O leaves rapidly from SO2 due to repulsion between negative charge of oxygen atom (H2O) and minus charge of SO2 . The distances at time = 96, 191, and 310 fs (points c, d, and e) were 3.924, 4.239, and 4.564 Å, respectively. Thus, H2O and SO2 anion gradually went away from each other. After all, the product leads to dissociation channel (R1 = 4.663 Å at 515 fs and point f). The intermolecular distance between SO2 and H2O (R1) is plotted in Figure 3A. Time profile of R1 showed that intermolecular distance (R1) increases from 2.88 to 4.24 Å (time = 0 to 191 fs). R1 reaches a peak at 191 fs (point d), and then it decreases from 4.24 to 3.50 Å. From the minimum point at 310 fs, the distance R1 linearly increases as a function of time. Time profile of R1 indicates that the complex anion leads to the dissociation products (SO2 + H2O) after the electron capture of (SO2)H2O. Potential energy of the system is plotted as a function of time in Figure 3B. Zero level corresponds to the energy at vertical

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Figure 4. Snapshots of SO2 (H2O)(Ar)2 following electron attachment of neutral complex 1:1:2 complex. Direct ab initio MD calculation was carried out at the MP2/6-311++G(d,p) level. Values indicate intermolecular distances between SO2 and H2O as r(O S) distance (in angstroms). Arrows schematically indicate displacement direction.

transition point in electron attachment to neutral complex (point a). After the electron capture, the energy of complex anion decreases gradually due to the rapid rotation of H2O and it is minimized at 41 fs (point b). This minimum is caused by dipole orientation of H2O to SO2 : the energy is stabilized by the orientation of protons of H2O to a minus charge of SO2 . The energy minima were also found at 99, 160, 202, 290, and 380 fs. However, the bottom of the energy minimum increases gradually due to H2O leaving SO2 . This result indicates that the (SO2 )H2O complex is dissociated to SO2 and H2O after the electron capture. The velocity of relative molecules is 1.2 10 2 Å/fs (2.4 kcal/mol), which is about 20% of the total available energy (Etotal = 13.1 kcal/mol). C. Effects of Argon Atoms on the Reaction Dynamics. In order to elucidate the effects of medium on the reaction dynamics, the electron capture process of SO2 H2O complex solvated by argon atoms were investigated. Two argon atoms were considered as solvent molecule in this section. The structure of (SO2 H2O)(Ar)2 was fully optimized at the MP2/6-311++G(d,p) level. The optimized structure (time = 0 and point a) and snapshots are illustrated in Figure 4. Each dipole of SO2 and H2O orients toward the argon atoms at the equilibrium point. The intermolecular distance (R1) is 2.865 Å, which is close to that of 1:1 complex SO2(H2O) (2.875 Å). The structure of SO2(H2O) moiety of SO2(H2O)(Ar)n is similar to that of (SO2)(H2O) without argon solvent, indicating that the effect of argon solvation on the structure of SO2(H2O) is 9093



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Figure 6. Result of direct ab initio MD calculation for electron capture of SO2(H2O)(Ar)2 1:1:2 complex. Snapshots and intermolecular distance are plotted as a function of time.

Figure 5. Result of direct ab initio MD calculation for electron capture of SO2(H2O)(Ar)2 1:1:2 complex: (A) intermolecular distance; (B) potential energy of the system. The corresponding snapshots are illustrated in Figure 4.

significantly small. The distances of r(S Ar) and r(O Ar) are calculated to be Rc = 4.092 Å and Ra = 3.712 Å, respectively, at time zero (point a). At 31 fs (point b), after the electron capture of (SO2 H2O)(Ar)2, H2O is leaving from SO2 and approaching to Ar(a). At 31 fs (point b), the intermolecular distance (R1) is 3.125 Å and distance of H2O from Ar(a) is 3.553 Å (0.16 Å shorter than that of point a). Both H2O and SO2 rotate as well as the dynamics of SO2 H2O without solvent. At 171 fs (point d), H2O collides with Ar(a): the SO2 is located at 4.378 Å from H2O (=R1) and the distance of Ar from H2O is Ra = 3.244 Å. After that, H2O is returned to SO2 . Finally, the anion complex (SO2 )H2O is formed at 218 (point e). At 417 fs (point f), one of the argon atoms, Ar(a), leaves the system, whereas Ar(b) still remains around the complex anion. Thus, this result suggests strongly that the collision of H2O with Ar atom enhances the formation of SO2 (H2O) complex. Potential energy of the system and intermolecular distances are plotted in Figure 5. After the electron capture of the 1:1:2 (SO2 H2O)(Ar)2 complex, the potential energy of the system vibrated periodically in the range 23 to 3 kcal/mol. The distance of H2O from SO2 (R1) increases with increasing

time (R1 = 2.8 4.4 Å) from time zero to point d (171 fs). On the othe hand, the distance of H2O from Ar(a) decreases from Ra = 3.712 Å (time = 0) to 3.244 Å (171 fs and point d). This result indicates that the H2O molecule leaves gradually from SO2 , while the H2O molecule approaches the Ar(a) atom. At 171 fs, the H2O molecule collides with Ar(b), and then it returned for the direction of SO2 due to the collision with Ar(a) atom. At 417 fs (point f), the anion molecule complex (SO2 )H2O was formed. This result indicates that the (SO2 )H2O complex is efficiently formed in the case of the electron capture existing in argon solvent. The atomic mass of argon atom is m = 40, which is two times heavier than that of H2O (m = 20). The mass of Ar atom is thus larger than that of H2O, so that H2O efficiently rebounds by the collision with the argon atom. Hence, SO2 (H2O) can be formed as a complex after the collision. This feature is much different from the electron capture of SO2(H2O) without solvent. From these results, it can be expected that the complex anionic (SO2 )H2O is formed in larger argon clusters. The anion molecule complex has a large amplitude motion corresponding to an intermolecular vibrational mode between SO2 and H2O. The excess energy generated by the reaction is flowing into the translational mode of Ar and intermolecular vibrational mode of the complex. A similar calculation was carried out for one argon system (SO2 )(H2O)(Ar)1. The product was a complex formation channel as well as two argon systems. Snapshots and potential energy are given in the Supporting Information. Therefore, it is concluded that only one argon atom affects the reaction dynamics of the SO2 H2O system. The (SO2)H2O(Ar)2 1:1:2 complex has another structural form as shown in Figure 6 (time zero). The argon atoms are located in the perpendicular position of the molecular axis of the (SO2)H2O complex. The distances of Ar atoms from SO2 and H2O are 3.884 and 3.664 Å, respectively. Time dependence of intermolecular distance between SO2 and H2O shows that the 9094



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Table 1. Optimized Geometrical Parameters of Neutral and Anion Complexes, SO2(H2O) and SO2 (H2O)a complex

parameter

MP2

QCISD

CCSD

SO2(H2O)

R1

2.875

2.839

2.838

R2 R3

1.469 0.961

1.451 0.959

1.447 0.959

θ

118.9

118.0

118.2

ϕ

103.9

104.3

104.3

R1

3.464

3.477

3.473

R2

1.540

1.535

1.531

R3

0.970

0.968

0.967

R4 θ

2.052 113.0

2.061 112.3

2.059 112.4

ϕ

97.4

97.9

97.8

SO2 (H2O)

a

Basis set used was 6-311++G(d,p). Bond lengths and angles are in angstroms and in degrees, respectively.

Table 2. Solvation Energies of the Reaction System (in kcal/ mol) and Available Energiesa reaction SO2 + H2O f SO2 (H2O) SO2 + H2O f SO2(H2O) [SO2 (H2O)]ver f SO2 + H2O

MP2

MP4SDQb

QCISD

CCSD

18.3

18.2

18.2

17.9

5.0

4.7

5.5

5.2

13.1

13.6

15.6

16.4

a The basis set used is 6-311++G(d,p). b Aug-cc-pVDZ basis set was used.

distance (R1) increases gradually with increasing time. After electron capture of the complex, the SO2 ion is dissociated from H2O. The distances between SO2 and H2O at 0.0, 400, and 700 fs are 2.881, 5.409, and 8.795 Å, respectively, indicating that the complex is directly decomposed after the electron capture. This result suggests the position of Ar atom around the complex is important in the case of electron capture dynamics. D. Structures and Energetics of the Present Systems. To check reliability of the level of theory used in the dynamics calculation, more accurate static ab initio calculations are carried out for stationary points. The optimized geometrical parameters of neutral complex and complex anion are given in Table 1. The calculations were carried out at the MP2, CCSD, and QCISD levels of theory with a 6-311++G(d,p) basis set. All calculations gave similar structures. The relative energies are calculated at several levels of theory, and the results are given in Table 2. The binding energy of the complex anion was calculated to be 18.6 kcal/mol at the QCISD/ 6-311++G(d,p) level. The MP2 calculation gives 18.3 kcal/mol for the energy. The vertical electron capture point [(SO2 )H2O] is 18.2 kcal/mol higher in energy than that of the dissociation limit (SO2 + H2O). The energy of a neutral complex, (SO2)H2O, is 5.0 kcal/mol relative to the dissociation limit (SO2 + H2O). The MP2 calculation gives reasonable energetics for the present system. From the accordance of the geometries, energetics, and harmonic vibrational frequencies, it can be strongly suggested that the MP2 calculation gives a reasonable potential energy surface for the neutral and anion systems of SO2 H2O. In an actual system, the structure of the complex fluctuated around the equilibrium point. To include the effects, geometrical

Figure 7. Schematic illustration of effects of “argon solvation” on the electron capture reaction of SO2(H2O) complex. The values indicate relative energies of molecules at stationary points calculated at the QCISD/6-311++G(d,p) level. The dashed line indicates a trajectory in argon solvation.

configurations of SO2 H2O were randomly selected, and then the trajectories were run. The calculation showed that all trajectories pass along the similar route up to the lowest energy points. (See Supporting Information.) These results indicate that trajectory starting from the optimized structure is a typical result.

4. DISCUSSION A. Reaction Model. A reaction model derived from the present study is schematically given in Figure 7. Upper and lower curves indicate neutral and anionic state potential energy curves (PECs), respectively. Horizontal axis indicates a reaction coordinate corresponding to the intermolecular distance between SO2 and H2O. In the neutral state (upper PEC), SO2 and H2O are bound as a binary complex SO2(H2O). The shape of PEC is purely attractive. The hatched region indicates a Franck Condon (FC) region for the electron capture of neutral complex. The lower potential energy curve indicates that anion complex SO2 H2O with the neutral structure is purely repulsive. On the other hand, a bound state of SO2 (H2O) is found if the structural relaxation takes place on the anionic potential energy surface. When electron capture occurs from the FC region, SO2 and H2O are dissociated from each other due to the repulsive interaction. The product after electron capture of SO2 H2O is the dissociation channel. On the other hand, the anion complex is formed if an argon atom exists near H2O. The collision of H2O with argon atoms induces the formation of a complex anion. The dotted line indicates a schematic illustration of trajectory of reaction point in the case of the SO2(H2O)Ar complex. The dissociated water molecule collides with an Ar atom, and then H2O returns to SO2 . Finally, SO2 (H2O) complex is formed as a product. 9095


The Journal of Physical Chemistry A The Ar atom escapes from the anion complex. On the other hand, the electron capture of SO2(H2O) without Ar atom leads to the dissociation product (SO2 + H2O). Thus, the present study clearly indicates that the Ar atom plays an important role in the electron capture dynamics of SO2(H2O). B. Summary of the Present Study. The present calculations can be summarized as follows. (1) An excess electron in (SO2 H2O) anion complex is distributed around the SO2 moiety. (2) Electron capture of a SO2(H2O) 1:1 complex gave a dissociation product, SO2 + H2O. (3) Electron capture of SO2(H2O)Ar 1:1:1 complex gives a binary complex anion SO2 (H2O), and the Ar atom is dissociated from the SO2 (H2O) anion complex after collision of H2O with the Ar atom. A similar result was obtained in the case of a 1:1:2 complex. (4) In the case of larger systems, SO2(H2O)(Ar)n, it is expected that the anion complex was formed after the collision of H2O with the Ar atom. Thus, the “solvent argon” plays an important role in formation of the complex anion.

’ ASSOCIATED CONTENT

bS

Supporting Information. Electron capture dynamics of SO2H2O(Ar) 1:1:1 complex, long range simulation of SO2 (H2O) (Ar)2, effects of initial conditions, all optimized structures of SO2(H2O)(Ar)n (n = 1 and 2), effects of basis set on the structures of SO2 H2O system. This material is available free of charge via the Internet at http://pubs.acs.org.

’ AUTHOR INFORMATION

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Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; and Pople, J. A. Gaussian 03, Revision B.04; Gaussian, Inc.: Wallingford, CT, 2004. (10) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, N. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, € Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; S.; Daniels, A. D.; Farkas, O.; Fox, D. J. Gaussian 09, Revision A.1; Gaussian, Inc.: Wallingford, CT, 2009. (11) Tachikawa, H.; Orr-Ewing, A. J. J. Phys. Chem. A 2008, 112, 11575. (12) Tachikawa, H. J. Phys. Chem. A 2010, 114, 4951. (13) Tachikawa, H. J. Phys. Chem. A 2010, 114, 4951. (14) Kondo, S.; Hashimoto, K.; Tachikawa, H. Chem. Phys. Lett. 2006, 431, 45.

Corresponding Author

*E-mail: [email protected].

’ ACKNOWLEDGMENT The author acknowledges partial support from a Grant-in-Aid for Scientific Research (C) from the Japan Society for the Promotion of Science (JSPS) (Project No. 21550002). ’ REFERENCES (1) Beard, K. V.; Bringi, V. N.; Thurai, M. Atmos. Res. 2010, 97, 395–415. (2) Cheyns, K; Mertens, J.; Diels, J.; Smolders, E.; Springael, D. Environ. Pollut. 2010, 158, 1405–1411. (3) Shukla, J. B.; Misra, A. K.; Naresh, R.; Chandr, P. Nonlinear Anal.: Real World Appl. 2010, 11, 2659–2668. (4) Wang, X.-B.; Yang, X.; Nicholas, J. B.; Wang, L.-S. Science 2001, 294, 1322. (5) Tarbuck, T. L.; Richmond, G. J. Am. Chem. Soc. 2005, 127, 16806. (6) Tarbuck, T. L.; Richmond, G. J. Am. Chem. Soc. 2006, 128, 3256. (7) Robertson, W. H.; Price, E. A.; Weber, J. M.; Shin, J.-W.; Weddle, G. H.; Johnson, M. A. J. Phys. Chem. A 2003, 107, 6527. (8) Woronowicz, E. A.; Robertson, W. H.; Weddle, G. H.; Johnson, M. A.; Myshakin, E. M.; Jordan, K. D. J. Phys. Chem. A 2002, 106, 7086. (9) 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.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; 9096


Collision Induced Complex Formation following Electron Capture of

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