DIPOLE-BOUND EXCITED-STATES OF THE I-CENTER-DOT-CH3CN AND I-CENTER-DOT(CH3CN)(2) ION-MOLECULE COMPLEXES - EVIDENCE FOR ASYMMETRIC SOLVATION

TY - JOUR

T1 - DIPOLE-BOUND EXCITED-STATES OF THE I-CENTER-DOT-CH3CN AND I-CENTER-DOT(CH3CN)(2) ION-MOLECULE COMPLEXES - EVIDENCE FOR ASYMMETRIC SOLVATION

AU - DESSENT, C E H

AU - BAILEY, C G

AU - JOHNSON, M A

PY - 1995/8/8

Y1 - 1995/8/8

N2 - Dipole-bound excited states are reported for the I- . CH3CN and I- .(CH3CN)(2) cluster ions, located just below their vertical electron detachment energies (determined using negative ion photoelectron spectroscopy). The absorption cross sections for excitation to these states are observed to increase with increasing dipole moments of the solvent molecules in the I- . M series (M=methyl iodide, acetone, acetonitrile). Photoexcitation at the peak of the transition to the dipole-bound state results exclusively in the dipole-bound fragment ion, M(-). The photoelectron spectrum of the (CHCN-)-C-3 fragment was also recorded by sequential two-photon absorption in the I- . CH3CN parent, indicating that the excess electron is indeed weakly bound (less than or equal to 10 meV) with very little intramolecular distortion evident upon electron detachment. The I- .(CH3CN)(2) cluster displays two absorption bands, one below each of the two features in the photoelectron spectrum. The most intense band correlates with the weaker, lower binding energy photoelectron band. Excitation of this strong absorption band results in production of both CH3CN- and (CH3CN)(2)(-) fragments, while excitation of the weaker absorption band only results in electron detachment. We interpret these results in the context of two structural isomers for I- .(CH3CN)(2): one with the solvent molecules surrounding the I- and another with both solvent molecules on the same side, asymmetrically solvating I- in a configuration with a large electric dipole moment in the neutral cluster over this anionic geometry. (C) 1995 American Institute of Physics.

AB - Dipole-bound excited states are reported for the I- . CH3CN and I- .(CH3CN)(2) cluster ions, located just below their vertical electron detachment energies (determined using negative ion photoelectron spectroscopy). The absorption cross sections for excitation to these states are observed to increase with increasing dipole moments of the solvent molecules in the I- . M series (M=methyl iodide, acetone, acetonitrile). Photoexcitation at the peak of the transition to the dipole-bound state results exclusively in the dipole-bound fragment ion, M(-). The photoelectron spectrum of the (CHCN-)-C-3 fragment was also recorded by sequential two-photon absorption in the I- . CH3CN parent, indicating that the excess electron is indeed weakly bound (less than or equal to 10 meV) with very little intramolecular distortion evident upon electron detachment. The I- .(CH3CN)(2) cluster displays two absorption bands, one below each of the two features in the photoelectron spectrum. The most intense band correlates with the weaker, lower binding energy photoelectron band. Excitation of this strong absorption band results in production of both CH3CN- and (CH3CN)(2)(-) fragments, while excitation of the weaker absorption band only results in electron detachment. We interpret these results in the context of two structural isomers for I- .(CH3CN)(2): one with the solvent molecules surrounding the I- and another with both solvent molecules on the same side, asymmetrically solvating I- in a configuration with a large electric dipole moment in the neutral cluster over this anionic geometry. (C) 1995 American Institute of Physics.

KW - DIOXIDE CLUSTER ANIONS

KW - NEGATIVE-IONS

KW - PHOTOELECTRON-SPECTROSCOPY

KW - PHOTODISSOCIATION SPECTROSCOPY

KW - CROSS-SECTIONS

KW - CARBON-DIOXIDE

KW - GAS-PHASE

KW - ATOMS

KW - CH3CN

KW - PHOTODETACHMENT

M3 - Article

SN - 0021-9606

VL - 103

SP - 2006

EP - 2015

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

IS - 6

ER -