Rotational conformers of m-methoxybenzyl radical in a supersonic jet

Abstract

The laser induced fluorescence (LIF) excitation spectrum of m-methoxybenzyl radical generated by ArF laser photolysis in a supersonic jet has been observed for the first time. The origin bands in the D₁ ← D₀ transition are found to be 19 993.0 cm⁻¹ and 19 648.3 cm⁻¹ for the cis and trans conformers, respectively, arising from the orientation of the methoxy group with respect to the methylene group at the meta position. The existence of the rotational conformers was ensured by analyzing the single vibronic level (SVL) dispersed fluorescence spectra with the aid of ab initio calculation. The prominent vibronic bands observed in the LIF excitation and SVL dispersed fluorescence spectra for each conformer were successfully assigned. A significant difference between the conformers was found for their band intensities and frequencies in the observed spectra. The difference will be discussed in terms of intramolecular interaction between the ring carbon atom and the hydrogen atom of the methoxy group.