Observation of vibronic emission spectrum of jet-cooled 3-chloro-4-fluorobenzyl radical.

We observed the vibronic emission spectrum of 3-chloro-4-fluorobenzyl radical using a corona-excited supersonic jet expansion (CESE) from the precursor 3-chloro-4-fluorotoluene. From an analysis of the observed spectrum, we investigate the formation of the 3-chloro-4-fluorobenzyl and 4-fluorobenzyl radicals and explained the reaction paths with an ab initio study. The D1 â†’ D0 transition energy and the frequencies of vibrational mode of the 3-chloro-4-fluorobenzyl radical were determined with a Franck-Condon simulation from density functional theory calculations in the D0 and D1 states.

Effect of chlorine dioxide in reduction of harmful microbes on fermented hot pepper paste.

In this study, the in vitro effects of chlorine dioxide (ClO2) in growth reduction against Candia glaebosa, Zygosaccharomyces bisporus, Saccharomycopsis capsularis and Pichia pastoris involving in deterioration of fermented hot pepper paste were studied to assess the applicability of chlorine dioxide to preparation of fermented hot pepper paste, and the concentration of ClO2 required for destruction of harmful microorganisms through the fumigation of fermented hot pepper paste was evaluated. ClO2 was treated by using ClO2 generator for 15 min. C. glaebosa, Z. bisporus and S. capsularis were reduced by ClO2 concentration dependent and not detected by ClO2 over 10 ppmV, whereas the P. pastoris was significantly perished by the treatment of ClO2 over 30 ppmV. We suggest that the ClO2 fumigation in stages of the preparation, disintegration, and fermentation of the paste made of fermented hot pepper might be useful for control of harmful microbes therein.

Spectroscopic evidence of jet-cooled o-chloro-alpha-methylbenzyl radical in corona excitation.

We report the first spectroscopic evidence of the o-chloro-alpha-methylbenzyl radical. The electronically hot but jet-cooled o-chloro-alpha-methylbenzyl radical was formed from precursor o-chloro-ethylbenzene seeded in a large amount of inert carrier gas helium, by employing the technique of corona excited supersonic expansion with a pinhole-type glass nozzle. The vibronic emission spectrum was recorded with a long path monochromator in the D(1) --> D(0) electronic transition in the visible region. By comparing the observed spectrum with that of the o-chlorobenzyl radical reported previously, we could easily identify the spectroscopic evidence of the jet-cooled o-chloro-alpha-methylbenzyl radical generated in the corona discharge of o-chloro-ethylbenzene, from which the electronic transition energy and several vibrational mode frequencies in the ground electronic state were accurately determined.

Observation of vibronic emission spectrum of jet-cooled duryl radical in corona excitation.

The vibronically excited but jet-cooled 2,4,5-trimethylbenzyl (duryl) radical was formed in a corona excitation from precursor 1,2,4,5-tetramethylbenzene (durene) seeded in a large amount of inert carrier gas helium using a pinhole-type glass nozzle. The vibronically resolved emission spectrum of the jet-cooled duryl radical was recorded, for the first time, with a long path monochromator in the visible region. The spectrum was analyzed to obtain an accurate electronic energy of the D1-->D0 transition and vibrational mode frequencies in the ground electronic state by comparing with those of the precursor and those from an ab initio calculation.

Vibronic spectroscopy of benzyl-type radicals: observation of mesityl radical in the gas phase.

We observed, for the first time, the vibronic emission spectrum of the jet-cooled mesityl radical that was formed from mesitylene seeded in a large amount of inert carrier gas helium using a pinhole-type glass nozzle in a corona excited supersonic expansion. The well-resolved vibronic emission spectrum was recorded in the visible region with a long path monochromator. The spectrum was analyzed to identify the origin of the D(2) --> D(0) and D(1) --> D(0) transitions as well as the frequencies of the vibrational modes in the ground electronic state of the mesityl radical by comparison with those of the known data of the precursor and an ab initio calculation.

Vibronic structure of jet-cooled 2,6-dimethylbenzyl radical: revisited.

We reexamined the vibronic structure of the jet-cooled 2,6-dimethylbenzyl radical that was generated from 1,2,3-trimethylbenzene seeded in a large amount of inert carrier gas helium using a pinhole-type glass nozzle in a corona excited supersonic expansion, from which the vibronically resolved emission spectrum was recorded with a long path double monochromator in the visible region. The spectrum exhibited bands arising from not only the D1 --> D0 transition but also the D2 --> D0 transition, in which transitions the accurate electronic energies of the D2 and D1 states and the revised vibrational mode frequencies in the ground electronic state were obtained by comparison with those from the known data of the precursor and an ab initio calculation.

3,4-dimethylbenzyl radical formed in a corona discharge of 1,2,4-trimethylbenzene.

A precursor, 1,2,4-trimethylbenzene, seeded in a large amount of an inert carrier gas, helium, was electrically discharged in a corona-excited supersonic expansion using a pinhole-type glass nozzle. The blue-green colored fluorescence emanating from the downstream jet was recorded with a long path monochromator to observe the vibronic emission spectrum of the benzyl-type radical formed. Analysis of the spectrum suggests that the most dominant product of the corona discharge is the 3,4-dimethylbenzyl radical formed by extracting a hydrogen atom from the methyl group at the 4-position. The electronic energies of the D1 and D2 states and the vibrational mode frequencies of the 3,4-dimethylbenzyl radical were accurately obtained for the first time by comparison with those from an ab initio calculation as well as those of the known vibrational mode frequencies of the precursor.