Laser Excitation Spectra of Large Alkoxy Radicals Containing 5−12 Carbon Atoms

Abstract

Laser induced fluorescence spectra of nearly 20 jet-cooled alkoxy free radicals, with up to 12 carbon atoms, have been observed. Trends, as a function of the number of carbon atoms, are reported for origin frequencies, and their dependence upon structural isomers are documented. The interpretation of various bands in the spectra, and their rotational contours, in terms of excited-state vibrations and/or different conformations is discussed.

Jet-cooled laser-induced fluorescence spectroscopy of methylcyclohexoxy radicals

“…The bands of other progressions are displaced to higher frequency with respect to each peak in progression A: y246 cm 21 higher for progression B, 379 cm 21 higher for progression C. The chair (e, e) conformer of cis-3-methylcyclohexoxy has a C 1 symmetry and the assignments of the vibronic bands are listed in Table 4. Band A is at 26 677 cm 21 , which is consistent with the calculated adiabatic excitation energy (26 664 cm 21 ) of the chair (e, e) conformer of cis-3-methylcyclohexoxy. The band (band A * ) at 683 cm 21 above the origin band has typical C-O stretch motion.…”

“…The lowest three electronic states X ˜, A ˜, and B ˜of alkoxy radicals were well defined in the literature. [19][20][21][22] The observed LIF spectra were the transition between the B ˜and X ˜states, which corresponds to the promotion of one electron from the s higher in frequency with respect to band A, is the swing motion (n 55 ) of the C-CH 3 and C-O bonds. But progression B possesses a same interval like progression A, which is the frequency of C-O stretch.…”

“…9,12,13 It is known that there are two types of conformer for cyclohexoxy, chair form and twisted-boat form. The twisted-boat conformers are y6 kcal mol 21 higher in energy than chair conformers. 9 Hence, only chair conformers are likely present under our experimental conditions.…”

“…The valve was operated in a continuous mode. The chamber vacuum was maintained using a molecular pump (600 L s 21 ) backed with a mechanical pump (8 L s 21 ). The initial vacuum was y3 6 10 23 Pa and increased to y7 Pa when injecting the sample.…”

Laster spectroscopic investigations of organic alkoxy and peroxy radicals.

“…That perception began to change when LIF spectra of iso-butoxy, 2-methyl -1-butoxy, isopentoxy t-pentoxy, 3-pentoxy, t-butoxy, and 2-butoxy were observed at near ambient temperature. [28][29][30][31] The reactions of alkoxy radicals in the atmosphere are significant and hence of great interest. The most important reactions are decomposition, reaction with O2 and isomerization.…”