Photoelectron Spectra of Substituted Benzenes

Abstract

Photoelectron spectra were measured in the region between 6 and 21 eV for aniline, N,N-dimethylaniline, phenol, anisole, benzonitrile, acetophenone, nitrobenzene, and their methyl derivatives. The observed spectra were interpreted in terms of their MO’s obtained by the CNDO/2 and EHMO methods, the methyl-substituent effect and the steric hindrance effect being considered. Both effects are essential for the reliable assignment of the observed photoelectron spectra. We found a general tendency that the interaction of the doubly degenerate highest occupied orbitals (e1g) of the benzene ring with the highest occupied orbital of a substituent group is important for the interpretation of the observed lower energy (7∼12 eV) bands. The only exceptional case is the nitrobenzenes in which the lowest vacant orbital of the substituent group is rather close to the highest occupied orbitals of the benzene ring and the interaction between them is important. The effects of the substituent groups upon the observed photoelectron spectra are classified into four types.

Selective Ionization of 2,4-Xylenol in Mass Spectrometry Using a Tunable Laser and Supersonic Jet Technique

“…Thus, the peak observed at 283.79 nm for 2,4-xylenol was located at the longest wavelength among these six xylenols. The ionization energy of 2,4-xylenol is reported to be 8.0 eV, 34 and the energy of the photon used for excitation at 283.79 nm and subsequent ionization is 4.37 eV. This suggests that 2,4-xylenol, as well as the other xylenols, can be efficiently ionized through a two-photon process.…”

Partial Ionization Cross Sections of Organic Molecules

“…Also available in the supplemental materials is a Perl-language script, "beb_tbl.pl," which reads a BUN file, applies the BEB theory, and produces a table of TICS as a function of incident electron energy. It is very similar to the script behind the NIST database [35]. For the present application, the only interesting value of the incident electron energy is 70 eV (1 eV ≈ 1.602 × 10 −19 J).…”

“…Acetophenone: For the highest orbitals, B/eV = 9.37, 9.55, 9.77, and 11.91 [35] replaced the CCSD(T) value of 9.38 and the P3 values of 9.59, 9.55, and 12.21, respectively.…”

Infrared multiphoton dissociation of the nitrobenzene cation

“…To explain all aspects of the observed formation of C5H5 + and C 6 H 5 0+ fragment ions from + nitrobenzene cations by IRMPD two different dissociation pathways leading to C 6 H 5 0 have been postulated. One produces stable C6H5 0ions and one leads to unstable C6H50 which further dissociates to C 5 On the other hand, it was argued that dissociation to produce C 6 H 5 + takes place from an excited electronic state, following removal of a bonding electron from the C-N bond upon ionization of the nitrobenzene neutral. …”