The laser photoelectron spectrum of gas phase aniline

Abstract

An effusive molecular beam of aniline vapor has been two-step ionized by irradiating it with the output from a frequency doubled dye laser. Photoelectrons ejected while exciting several different vibronic levels of its 1B2 electronic state have been kinetic energy analyzed. In all cases ions are found to be generated in their ground electronic state. Their vibrational state distribution is strongly wavelength dependent and differs remarkably from that obtained in conventional single photon photoelectron spectroscopy. The energies of several in-plane vibrational modes of aniline cations have been measured. In contrast with the ground electronic state of the neutral molecule, the ground state of the ion and 1B2 excited electronic state of the neutral molecule both appear to be nearly planar.

High resolution threshold photoelectron spectroscopy of aniline and aniline van der Waals complexes

“…This mode is 390 cm -I in So and from the observation of the 156 transition (703 cm-I ) it is estimated to be 351 cm-I in SI' This particular transition was not pumped by Meek et al 11 and they have not offered an assignment for the VIS band in the ion. Wallace et al 13 ,14 have scanned the PIE with the 15 2 level as an intermediate state and determined VIS to be 72~ cm -I.…”

“…We choose to assign the more intense feature at 1102 to the ~v=O transition 15~+, which gives an estimate of VIS as 551 cm -I. We do not have a definite assignment for the second feature, but Meek et al 11 have suggested that 9ab+ could be assigned to this frequency. As suggested by Wallace et al it is reasonable to expect a large increase in VIS upon ionization due to the Sp2 hybridization of the nitrogen in the aniline cation and the strengthening of the phenyl-nitrogen bond due to increased double bond character.…”

Substituent effects on ultrafast excited-state proton transfer of protonated aniline derivatives in aqueous solution

“…1. The amino nitrogen of ANs in the ground-state possesses sp 3 -like configuration with almost pyramidal structure, while upon electronic excitation the configuration of the amino group changes to sp 2 like with more planar structure [18,19]. Such structural change of the amino group in the S 1 state results in charge migration from the amino group to the benzene ring, leading to enhancement of the acidity of its protonated form in the excited state [20].…”

Time-delayed two-color photoelectron spectra of aniline, 2-aminopyridine, and 3-aminopyridine: Snapshots of the nonadiabatic curve crossings

“…The out-of-plane bending angle of the amino hydrogens in the ground state is 42°, 34,35 and decreases to almost zero upon excitation to the S 1 electronic state. 27,36 Several early twophoton ionization experiments 28,37 and recent high resolution photoelectron spectra 23,33 have shown that the aniline cation in the 2 B 1 ground state has an almost planar structure. Photoelectron spectra showing vibrational structure in the excited electronic state 2 A 2 of the cation have recently been reported.…”