Cation Vibrations of 1-Methylnaphthalene and 2-Methylnaphthalene through Mass-Analyzed Threshold Ionization Spectroscopy

Abstract

Vibrationally resolved cation spectra of 1-methylnaphthalene (1MN) and 2-methylnaphthalene (2MN) were obtained using the two-color resonant two-photon mass-analyzed threshold ionization (MATI) spectroscopy. MATI spectra were obtained through ionization via several intermediate vibronic levels. Due to hindrance effect, no spectral features related to methyl torsion were observed in the MATI spectra of 1MN. By contrast, most of the in-plane ring deformation vibrations of the 2MN cation were found to couple with methyl torsion because of its small internal rotational barrier. These experimental findings were well supported by our theoretical calculations.

VUV photoprocessing of oxygen-containing polycyclic aromatic hydrocarbons: Threshold photoelectron spectra

“…In addition to IE determinations, we have employed threshold photoelectron spectra with imaging electron detection at the Swiss Light Source to study the photoelectron spectra of PAHs (naphthalene, anthracene, and pyrene) [9] and hydrogenated PAHs (dihydro-naphthalene andanthracene and tetralin) [9][10][11]. Kong and co-workers have employed the zero-kinetic-energy pulsed-field ionization (ZEKE-PFI) approach to explore ionization in pentacene [12] and benzoquinoline [13], while Tzeng employed the related mass-analyzed threshold ionization (MATI) method for methyl-substituted naphthalenes [14]. Larger PAHs and their clusters, which are more relevant models for PAHs in the ISM, have been explored at the Soleil synchrotron [15][16][17].…”