Jet Spectroscopy of theD122B1–D012B1Transition of thep-Cyanobenzyl Radical

Rotational conformers of m-methoxybenzyl radical in a supersonic jet

“…The energy shift for m-methoxybenzyl radical was found to be much larger than those of mfluorobenzyl and m-chlorobenzyl radicals. The D 1 origin of p-cyanobenzyl radical 16 was reported to be at 20 738 cm À1 and the red-shifted energy was approximately 1300 cm À1 , which was the largest among the mono-substituted benzyl radicals. [14][15][16][20][21][22] Tokumura et al observed the absorption spectra of p-methoxybenzyl and p-cyanobenzyl radicals in hexane solution at room temperature.…”

“…The D 1 origin of p-cyanobenzyl radical 16 was reported to be at 20 738 cm À1 and the red-shifted energy was approximately 1300 cm À1 , which was the largest among the mono-substituted benzyl radicals. [14][15][16][20][21][22] Tokumura et al observed the absorption spectra of p-methoxybenzyl and p-cyanobenzyl radicals in hexane solution at room temperature. 25,26 The absorption band is red-shifted relative to that of the p-cyanobenzyl radical.…”

“…The low-frequency bands appearing up to about 400 cm À1 from the origin of m-methylanisole in the excitation spectrum are attributed to the internal rotation of the methyl group attached to the benzene ring, 11 while such low-frequency bands do not appear for m-methoxybenzyl radical and other benzyl-type radicals. [14][15][16][17][18][19][20][21][22] The most intense band (band II) observed at 19 993.0 cm À1 has intensity about 5 times that of band I. The relative intensity did not depend on the variations in the Ar backing pressure (1-3 atm).…”

“…Recently, the rotational conformers were also found in the cationic states by PFI-ZEKE spectroscopy. 12 As the fundamental aromatic p radical belonging to one of the odd alternate hydrocarbons, benzyl radical has spawned both experimental [13][14][15][16][17][18][19][20][21][22] and theoretical 23 studies over the past four decades. Most of the work has been focused on the vibronic coupling interaction between the excited electronic states, 2 A 2 and 2 B 1 .…”

“…The strong coupling causes an unusually complicated vibronic structure and a weak oscillator strength in the lowest transition, which was assigned to the D 1 1 2 A 2 -D 0 1 2 B 1 transition by Cossart-Magos and Leach 13 from a rotational contour analysis of the emission spectrum. Later, wellresolved spectra of jet-cooled benzyl radical and its derivatives were obtained by applying LIF, [14][15][16][17] REMPI, 18 and emission [19][20][21][22] spectroscopy.…”