Penning ionization of (CH3)4C and (CH3)3CCl by collision with He*(2 3S) metastable atoms

Abstract

Penning ionization of (CH3)4C and (CH3)3CCl upon collision with He*(2 3S) metastable atoms were studied by angular and collision-energy resolved Penning ionization electron spectroscopy. The observed Penning ionization electron spectra (PIES) revealed peculiar features for the totally symmetric ionized state of the target molecules which can be ascribed to ionization from a molecular orbital having carbon 2s atomic orbital characters; (1) the relative PIES intensity is extremely enhanced, (2) the intensity distribution of the vibrational fine structure in PIES is clearly different from that observed for ultraviolet photoelectron spectra, (3) the angular distribution of Penning electrons is highly isotropic, and (4) the collision energy dependence of the partial Penning ionization cross section is slightly increasing and rather flattened with respect to the increase of the collision energy. These features were found to be due to the formation of an excimer-like state involving C2s hole characters in the target molecule which induces Auger-like transitions selectively from orbitals having the C2s characters. Effects of attractive interaction potentials were observed for (CH3)3CCl on the ionized state ascribed to the Cl nonbonding orbital.

Spin−Orbit Coupling Effect and Intramolecular Orbital Interactions: Penning Ionization of CH2BrCl, CHBrCl2, and CH2BrCN by Collision with He*(23S) Metastable Atoms

“…12,14-17 Band 9 in Figure 2 is enhanced significantly in the PIES with respect to that in the UPS because the corresponding 20a′ orbital has some characteristics of C 2s orbital (see Figure 8), and it has been noted that the resonant excitation transfer and the subsequent autoionization frequently occurs for the C 2s bands. 10 The S* and S(S*) bands have been observed clearly in the PIES of Figures 1, 2, 4, and 5. They may not belong to the satellite states related to shake-up or shake-off processes, because no similar bands were observed at the same energy regions in the photoelectron spectra by the synchrotron radiation 31 and He II radiation.…”

An overlap expansion method for improving ab initio model potentials: Anisotropic intermolecular potentials of N2, CO, and C2H2 with He*(2 3S)

“…[9][10][11][12]16 A metastable beam of He was produced by a nozzle discharge source, and the He*(2 1 S) component was quenched by a water-cooled helium discharge lamp. The metastable He*(2 3 S) beam was pulsed by a mechanical chopper and then introduced into a collision cell located 504 mm downstream from the chopper disk.…”

“…8 Coupled experimental techniques including ve-locity selection and electron kinetic energy analysis of Penning ionization have been developed. [9][10][11][12][13][14][15] Recently, these techniques further developed to give collision energy/ electron energy resolved two-dimensional Penning ionization electron spectra ͑2D-PIES͒, 16 from which we can obtain ͑a͒ collision energy resolved Penning ionization electron spectra ͑CERPIES͒ and ͑b͒ collision energy dependence of partial Penning ionization cross sections ͑CEDPICS͒ for all final ionic states. For molecular targets, each CEDPICS for a particular final ionic state reflects the interaction potential in the region where the corresponding molecular orbital extends, therefore anisotropy of interaction potentials between molecules and excited atoms can be studied from CEDPICS.…”

Desorption Flame-Induced Atmospheric Pressure Chemical Ionization Mass Spectrometry for Rapid Real-World Sample Analysis

“…[1][2][3] e metastable atom or molecule, such as He * and N 2 * , can react with the analytes through Penning ionization processes to form radical cation of analyte. [4][5][6] To generate primary ions and metastable species for APCI processes, several approaches have been developed. 1,[7][8][9][10][11][12][13][14] e electric discharge-based technique is the most used APCI method, where various reactive species are generated in an electric discharging region under ambient conditions.…”

“…[1][2][3][4][5][6] e proton or charge in the primary ion are transferred to the analyte to form analyte ion. [1][2][3] e metastable atom or molecule, such as He * and N 2 * , can react with the analytes through Penning ionization processes to form radical cation of analyte.…”