Excitation energies, photoionization cross sections, and asymmetry parameters of the methyl and silyl radicals

Abstract

Vertical excitation energies of the methyl and silyl radicals were inferred from ab initio electron propagator calculations on the electron affinities of CH 3 + and SiH 3 + . Photoionization cross sections and angular distribution of photoelectrons for the outermost orbitals of both CH 3 and SiH 3 radicals have been obtained with the Molecular Quantum Defect Orbital method. The individual ionization cross sections corresponding to the Rydberg channels to which the excitation of the ground state's outermost electron gives rise are reported. Despite the relevance of methyl radical in atmospheric chemistry and combustion processes, only data for the photon energy range of 10-11 eV seem to be available. Good agreement has been found with experiment for photoionization cross section of this radical. To our knowledge, predictions of the above mentioned photoionization parameters on silyl radical are made here for the first time, and we are not aware of any reported experimental measurements. An analysis of our results reveals the presence of a Cooper minimum in the photoionization of the silyl radical. The adequacy of the two theoretical procedures employed in the present work is discussed.

CaH Rydberg series, oscillator strengths and photoionization cross sections from Molecular Quantum Defect and Dyson Orbital theories

“…A Cooper minimum, which is a useful phenomenon for analyzing photoelectron dynamics [24], is found in our calculated cross sections. Cooper minima also have been observed in previous applications of the MQDO method to molecular photoionization studies [25,26]. To our knowledge neither theoretical nor experimental continuum transition intensities of CaH have been reported.…”

Photoionization cross sections and asymmetry parameters for ethanol. A theoretical study

“…In particular, we have calculated photoionization cross-sections for specific ionic states of methyl radical [16], methanol [17], acetone [18] and formaldehyde [19]. Motivated by the good results we have obtained for these molecules, it is the purpose of the present study to supply partial photoionization crosssection data of ethanol at photon energies where these data are unavailable.…”