TY - JOUR

T1 - Vibrational spectroscopy of (SO2-4 ) · (H 2O)n clusters, n=1-5

T2 - Harmonic and anharmonic calculations and experiment

AU - Miller, Yifat

AU - Chaban, Galina M.

AU - Zhou, Jia

AU - Asmis, Knut R.

AU - Neumark, Daniel M.

AU - Benny Gerber, R.

N1 - Funding Information:
This research was supported by the U.S.-Israel Binational Science Foundation (BSF-2004009). It is also supported by NSF through the EMSI at UC Irvine (Grant No. 0431312), CRC project (0209719), and by a grant from the state of Lower Saxony and the Volkswagen Foundation, Hannover, Germany. One of the authors (D.M.N.) acknowledges support from the Air Force Office of Scientific Research under Grant No. F49620-03-1-0085. Two of the authors (K.R.A. and G.S.) gratefully acknowledge the support of the Stichting voor Fundamental Onderzoek der Materie (FOM) in providing the required beam time on FELIX and highly appreciate the skillful assistance of the FELIX staff. They also thank the Deutsche Forschungsgemeinschaft for support as part of the GK788 and the SFB546.

PY - 2007/9/13

Y1 - 2007/9/13

N2 - The vibrational spectroscopy of (S O4 2-) (H2 O)n is studied by theoretical calculations for n=1-5, and the results are compared with experiments for n=3-5. The calculations use both ab initio MP2 and DFT/B3LYP potential energy surfaces. Both harmonic and anharmonic calculations are reported, the latter with the CC-VSCF method. The main findings are the following: (1) With one exception (H2 O bending mode), the anharmonicity of the observed transitions, all in the experimental window of 540-1850 cm-1, is negligible. The computed anharmonic coupling suggests that intramolecular vibrational redistribution does not play any role for the observed linewidths. (2) Comparison with experiment at the harmonic level of computed fundamental frequencies indicates that MP2 is significantly more accurate than DFT/B3LYP for these systems. (3) Strong anharmonic effects are, however, calculated for numerous transitions of these systems, which are outside the present observation window. These include fundamentals as well as combination modes. (4) Combination modes for the n=1 and n=2 clusters are computed. Several relatively strong combination transitions are predicted. These show strong anharmonic effects. (5) An interesting effect of the zero point energy (ZPE) on structure is found for (S O4 2-) (H2 O)5: The global minimum of the potential energy corresponds to a Cs structure, but with incorporation of ZPE the lowest energy structure is C2v, in accordance with experiment. (6) No stable structures were found for (O H-) (HS O4-) (H2 O)n, for n≤5.

AB - The vibrational spectroscopy of (S O4 2-) (H2 O)n is studied by theoretical calculations for n=1-5, and the results are compared with experiments for n=3-5. The calculations use both ab initio MP2 and DFT/B3LYP potential energy surfaces. Both harmonic and anharmonic calculations are reported, the latter with the CC-VSCF method. The main findings are the following: (1) With one exception (H2 O bending mode), the anharmonicity of the observed transitions, all in the experimental window of 540-1850 cm-1, is negligible. The computed anharmonic coupling suggests that intramolecular vibrational redistribution does not play any role for the observed linewidths. (2) Comparison with experiment at the harmonic level of computed fundamental frequencies indicates that MP2 is significantly more accurate than DFT/B3LYP for these systems. (3) Strong anharmonic effects are, however, calculated for numerous transitions of these systems, which are outside the present observation window. These include fundamentals as well as combination modes. (4) Combination modes for the n=1 and n=2 clusters are computed. Several relatively strong combination transitions are predicted. These show strong anharmonic effects. (5) An interesting effect of the zero point energy (ZPE) on structure is found for (S O4 2-) (H2 O)5: The global minimum of the potential energy corresponds to a Cs structure, but with incorporation of ZPE the lowest energy structure is C2v, in accordance with experiment. (6) No stable structures were found for (O H-) (HS O4-) (H2 O)n, for n≤5.

UR - http://www.scopus.com/inward/record.url?scp=34548487474&partnerID=8YFLogxK

U2 - 10.1063/1.2764074

DO - 10.1063/1.2764074

M3 - Article

C2 - 17824737

AN - SCOPUS:34548487474

SN - 0021-9606

VL - 127

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

IS - 9

M1 - 094305

ER -