Vacuum ultraviolet laser pulsed field ionization-photoelectron study of cis-dichloroethene

Abstract

The vacuum ultraviolet (VUV) laser pulsed field ionization photoelectron (PFI-PE) spectrum of cis-dichloroethene (cis-ClCH[Double Bond]CHCl) has been measured in the energy region of 77 600-79 500 cm(-1). On the basis of the semiempirical simulation of the origin PFI-PE band, we have obtained the IE(cis-ClCH[Double Bond]CHCl) to be 77 899.5+/-2.0 cm(-1) (9.658 39+/-0.000 25 eV). The assignment of the vibrational bands resolved in the VUV-PFI-PE spectrum are guided by high-level ab initio calculations of the vibrational frequencies for cis-ClCH[Double Bond]CHCl(+) and the Franck-Condon factors for the ionization transitions. Combining the results of the present VUV-PFI-PE measurement and the recent VUV-infrared-photoinduced Rydberg ionization study, the vibrational frequencies for eleven of the twelve vibrational modes of cis-ClCH[Double Bond]CHCl(+) have been experimentally determined: nu(1) (+)(a(1))=181 cm(-1), nu(2) (+)(a(2))=277 cm(-1), nu(3) (+)(b(2))=580 cm(-1), nu(4) (+)(b(1))=730 cm(-1), nu(5) (+)(a(1))=810 cm(-1), nu(6) (+)(a(2))=901 cm(-1), nu(8) (+)(a(1))=1196 cm(-1), nu(9) (+)(b(2))=1348 cm(-1), nu(10) (+)(a(1))=1429 cm(-1), nu(11) (+)(b(2))=3067 cm(-1), and nu(12) (+)(a(1))=3090 cm(-1)). These values are compared to theoretical anharmonic vibrational frequencies obtained at the MP2/6-311G(2df,p) and CCSD(T)/6-311G(2df,p) levels. The IE prediction for cis-ClCH[Double Bond]CHCl has also been calculated with the wave function based CCSD(T)/CBS method, which involves the approximation to the complete basis set (CBS) and the high-level correlation corrections. The theoretical IE(cis-ClCH[Double Bond]CHCl)=9.668 eV thus obtained is found to have a deviation of less than 10 meV with respect to the experimental IE value.

Infrared Vacuum-Ultraviolet Laser Pulsed Field Ionization-Photoelectron Study of CH3Br+(X̃2E3/2)

“…The VUV-PIE spectra display a step-like onset with negligible autoionization structures above the onset. According to the accepted procedures for IE determination based on the VUV-PIE measurement, the IE of CH 3 Br can be reliably determined by the energy [marked by the downward-pointing arrow at the top of the PIE step in Figure a] at which the PIE onset exhibits the largest decrease in slope. As shown in this figure, the IEs for CH 3 79 Br and CH 3 81 Br thus determined by the two PIE curves are indistinguishable and have the value of 85 028 ± 2 cm −1 .…”

“…In order to determine more precise IE values, we have previously employed a semi-empirical simulation scheme to simulate the VUV-PFI-PE origin bands observed for many polyatomic species which exhibit only minor rotational structures. – The major assumption adopted in this semi-empirical simulation scheme is that the PI cross sections for all the J transitions associated with a given Δ J + branch are taken to have the same value. In addition to this assumption, the semi-empirical simulation scheme also assumes that the intensities for all possible PI rotational transitions are proportional to the initial rotational population of the neutral molecule according to the Boltzmann distribution.…”

“…The arrangement of the IR-VUV laser photoion-PE apparatus and experimental procedures used for VUV-phototionization efficiency (VUV-PIE), VUV-PFI-PE, IR-VUV-PI, and IR-VUV-PFI-PE measurements have been described in detail previously. – ,– Briefly, the apparatus consists of a pulsed (30 Hz) tunable VUV-laser system, a pulsed (30 Hz) molecular-beam source, a TOF electron spectrometer for PFI-PE detection, and a TOF mass spectrometer for ion detection. The electron spectrometer and mass spectrometer are each equipped with a microchannel plate (MCP) detector for the detection of electrons and ions, respectively.…”

An experimental and theoretical study of the photoelectron spectra of cis-dichloroethene: Valence shell vertical ionization and vibronic coupling in the low-lying cationic states

“…Of relevance to the present work are photoelectron spectra of dichloroethene recorded with HeI, [21][22][23][24][25] HeII, 25 Al K↵, 26 and synchrotron 27,28 radiation. Mass analyzed threshold ionization (MATI) 29 and pulsed field ionization photoelectron (PFI-PE) 30 spectra have been reported. Electron momentum spectroscopy has also been employed.…”

Photoionization dynamics of cis-dichloroethene from investigation of vibrationally resolved photoelectron spectra and angular distributions

“…Previous experimental investigations on cis-dichloroethene include photoelectron spectra recorded with HeI [22][23][24][25][26] HeII, 26 Al K↵, 27 and synchrotron 28 radiation, mass analyzed threshold ionization (MATI) 29 and pulsed field ionization photoelectron (PFI-PE) 30 spectra of the ground ionic state, and electron momentum spectroscopy. 31 Fragmentation studies have also been performed.…”