Vacuum Ultraviolet (VUV) Pulsed Field Ionization−Photoelectron and VUV−IR Photoinduced Rydberg Ionization Study of trans-Dichloroethene

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2004-11, Vol.108 (45), p.9637-9644
• Main Authors: Woo, H. K, Wang, P, Lau, K. C, Xing, X, Ng, C. Y
• Format: Article
• Language: English
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp040250s

The vacuum ultraviolet (VUV) pulsed field ionization−photoelectron (PFI−PE) spectrum for trans-dichloroethene (trans-ClCHCHCl) has been measured in the energy range 77 600−79 200 cm-1. On the basis of the spectral simulation of the origin VUV−PFI−PE vibrational band, we have determined the IE(trans-ClCHCHCl) to be 77 678.4 ± 2.0 cm-1 (9.630 97 ± 0.000 25 eV). The vibrational bands resolved in the VUV−PFI−PE spectrum of trans-ClCHCHCl are assigned on the basis of ab initio vibrational frequencies and calculated Franck−Condon factors for the ionization transitions, yielding eight vibrational frequencies ν1 + = 163 cm-1, ν3 + = 367 cm-1, ν4 + = 871 cm-1, ν5 + = 915 cm-1, ν6 + = 944 cm-1, ν8 + = 1235 cm-1, ν9 + = 1258 cm-1, ν10 + = 1452 cm-1. The distinct feature of the VUV−PFI−PE spectrum is the strong vibrational progression of the ν3 + (CCl stretching) mode of trans-ClCHCHCl+, which is consistent with the theoretical geometry calculation, predicting a significant change in the CCl bond distance upon photoionization of trans-ClCHCHCl. We have also determined the frequency (3068 cm-1) for the ν11 + (CH stretching) vibrational mode of trans-ClCHCHCl+ by employing the VUV−IR-photoinduced Rydberg ionization (VUV−IR−PIRI) method. The VUV−IR−PIRI spectra for trans-ClCHCHCl prepared in the effective principal quantum numbers, n* = 14 and 36, are found to be identical, supporting the previous conclusion that the Rydberg electron behaves as a spectator; i.e., the Rydberg electron orbital is conserved during the IR excitation of the ion core.