Corona Excited Supersonic Expansion Research Articles

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 → 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.

Heart Rate Recovery and Cardiovascular Risk Factors among Firefighters

We report the vibronic emission spectrum of 4-chloro-m-xylyl radical using a long-path monochromator in a corona-excited supersonic expansion (CESE). By the precursor 4-chloro-m-xylene, we identified 4-chloro-m-xylyl from the two isomeric benzyl-type radicals analyzing a Franck-Condon simulation and ab initio calculations. From an analysis of the vibronic emission spectrum of the 4-chloro-m-xylyl radical, the D1 → D0 electronic transition energy was confirmed and the assignments of vibrational frequencies were accomplished in the ground state.

Observation of vibronic emission spectrum of jet-cooled 4-chloro-m-xylyl radical

We report the vibronic emission spectrum of 4-chloro-m-xylyl radical using a long-path monochromator in a corona-excited supersonic expansion (CESE). By the precursor 4-chloro-m-xylene, we identified 4-chloro-m-xylyl from the two isomeric benzyl-type radicals analyzing a Franck-Condon simulation and ab initio calculations. From an analysis of the vibronic emission spectrum of the 4-chloro-m-xylyl radical, the D1 → D0 electronic transition energy was confirmed and the assignments of vibrational frequencies were accomplished in the ground state.

Spectroscopic identification of the p-ethylbenzyl radical in a corona-excited supersonic expansion

The excitation spectrum of the jet-cooled p-ethylbenzyl radical was generated from the precursor 1,4-diethylbenzene in a corona-excited supersonic expansion (CESE). Assignment of the p-ethylbenzyl radical was confirmed by comparing the spectra from p-xylene and p-ethyltoluene. The geometry optimization and vibrational frequencies of the p-ethylbenzyl radical were computed with density functional calculation. Conclusive vibronic band assignment was analyzed with a Franck-Condon simulation in the D0 − D1 transition.

Jet-cooled spectroscopy of the m-ethylbenzyl radical in a corona-excited supersonic expansion.

The vibronic structure of m-ethylbenzyl radical has been investigated in the gas phase for the first time in a corona-excited supersonic expansion (CESE). Assignment of the m-ethylbenzyl radical has been reported by comparing the spectra from m-xylene and m-ethyltoluene. The theoretical calculation, Density functional theory, of the D0 and D1 state structures of the m-ethylbenzyl radical was computed. Conclusive assignment of vibronic emission spectrum has been analyzed with an aid of Franck-Condon simulation in the D0-D1 transition.

Jet-cooled spectroscopy of the isomeric chloro-p-xylyl radicals in a corona-excited supersonic expansion

We report the jet-cooled isomeric chloro-p-xylyl radicals in a corona-excited supersonic expansion (CESE), and its vibronic spectrum was recorded with a long-path monochromator. By the precursor 2-chloro-p-xylene, we identified the two isomeric benzyl-type radicals, 2-chloro-p-xylyl and 3-chloro-p-xylyl radicals in the corona discharge. The vibronic emission spectrum of the chloro-p-xylyl radicals corresponded to the D1 → D0 electronic transition and determined the electronic transition energy depending on the constitutional isomers.

Visible emission spectroscopy of jet-cooled chloro-substituted 2-methylbenzyl radicals

Four isomeric chloro-substituted 2-methylbenzyl radicals were generated from the corona discharge of 3- and 4-chloro-o-xylenes seeded in a large amount of He carrier gas using a technique of corona excited supersonic expansion coupled with a pinhole-type glass nozzle. The observed visible vibronic emission spectra were analyzed to identify the radical species produced in the discharge, from which the production of the 3-, 4-, 5-, and 6-chloro-2- methylbenzyl radicals was confirmed. In addition, we determined the D1 → D0 electronic transition energies and vibrational mode frequencies in the D0 state of the isomeric chloro-substituted 2-methylbenzyl radicals.

Spectroscopic identification of jet-cooled o-ethynylbenzyl radical generated in corona discharge

The vibronically excited but jet-cooled o-ethynylbenzyl radical was generated from precursor, o-ethynyltoluene seeded in a large amount of carrier gas helium using a home-made pinhole-type glass nozzle combined with the technique of corona excited supersonic expansion. The visible vibronic emission spectrum was recorded with a long-path monochromator from the corona discharge of the precursor. By analyzing the observed spectrum, we determined the electronic energy in the D1 → D0 transition and vibrational mode frequencies in the D0 electronic state of the o-ethynylbenzyl radical.

Spectroscopic evidence of α,α-dimethylbenzyl radicals in the gas phase

We report the spectroscopic evidence of the jet-cooled α,α-dimethylbenzyl radical, which was generated in a technique of corona excited supersonic expansion using a pinhole-type glass nozzle. For identification of the α,α-dimethylbenzyl radical, precursors that form a common molecular radical, as a result of dissociation of either a CH bond or CC bond of alkyl group in a corona discharge, were employed. Based on comparisons of the spectra observed from the corona discharges of isopropylbenzene and tert-butylbenzene, evidence was obtained of the existence of the α,α-dimethylbenzyl radical in the gas phase.

Electronic emission spectroscopy of the 4-methyl-3-azabenzyl radical

The 4-methyl-3-azabenzyl radical was generated from 2,5-lutidine in a corona excited supersonic expansion, and its fluorescence emission spectrum was recorded. Two possible radical isomers could form by loss of an H atom from either methyl group in 2,5-lutidine. Theoretical studies of both isomers confirmed the only species observed was 4-methyl-3-azabenzyl. The emission spectrum corresponded to the D1→D0 transition, with a strong origin peak and several vibronic bands. The origin transition is located at 21401cm−1, in good agreement with a previous assignment, and calculated vibrational energies were in good agreement experimental vibrational energies.

Vibronic emission spectrum of 2-chloro-6-fluorobenzyl radical produced in corona discharge

We generated vibronically excited but jet-cooled 2-chloro-6-fluorobenzyl radical from precursor 2-chloro-6-fluorotoluene seeded in a large amount of helium carrier gas using a pinhole-type glass nozzle coupled with a technique of corona excited supersonic jet expansion. From an analysis of the visible vibronic emission spectrum observed, we found evidence of the formation of the 2-chloro-6-fluorobenzyl and 2-fluorobenzyl radicals, and determined the electronic energy in the D1→D0 transition and the vibrational mode frequencies of the 2-chloro-6-fluorobenzyl radical in the ground electronic state, for the first time, by comparison with ab initio calculations of the precursor molecule.

Spectroscopic evidence of α,α-dichlorobenzyl radical produced by corona discharge of benzotrichloride

We report spectroscopic observations of the α,α-dichlorobenzyl radical obtained by corona excited supersonic jet expansion using a pinhole-type glass nozzle. Vibronically excited but jet-cooled radicals were generated by corona discharge of the precursor benzotrichloride with a large amount of helium carrier gas, from which the visible vibronic emission spectrum was recorded using a long path monochromator. From an analysis of the spectrum observed, the electronic energy of the D1→D0 transition and a few vibrational mode frequencies in the ground electronic state were obtained for the α,α-dichlorobenzyl radical by comparing observed frequencies with those obtained by ab initio calculation.

Vibronic emission spectroscopy of benzyl-type radicals: Jet-cooled 2-fluoro-5-chlorobenzyl radical

We produced the vibronically excited but jet-cooled 2-fluoro-5-chlorobenzyl radical by corona discharge of precursor 2-fluoro-5-chlorotoluene with a large amount of carrier gas He using a pinhole-type glass nozzle in a technique of corona excited supersonic jet expansion. The vibronic emission spectrum was recorded using a long-path double monochromator in the visible region. From an analysis of the spectrum, we determined the electronic energy of the D1→D0 transition and vibrational mode frequencies in the ground electronic state of the 2-fluoro-5-chlorobenzyl radical for the first time. In addition, substituent effect on electronic transition energy was discussed for substituents on the benzene ring.

Vibronic spectroscopy of dichlorobenzyl radicals: Jet-cooled 3,4-dichlorobenzyl radical

By means of a technique of corona excited supersonic expansion coupled with a pinhole-type glass nozzle, vibronically excited but jet-cooled 3,4-dichlorobenzyl radical was formed from precursor 3,4-dichlorotoluene in corona discharge. From an analysis of the visible vibronic emission spectrum observed, we determined the electronic energy of the D1→D0 transition and vibrational mode frequencies in the D0 state of the 3,4-dichlorobenzyl radical by comparing with the known vibrational data of precursor and an ab initio calculation. Also, the substituent effect on the electronic transition energy was explained using Hückel’s molecular orbital theory for the first time.

Spectroscopic Evidence of Jet-Cooled p-Chloro-α-Methylbenzyl Radical in Corona Excitation

We report the first spectroscopic evidence of the jet-cooled p-chloro-<TEX>${\alpha}$</TEX>-methylbenzyl radical. The visible vibronic emission spectrum was recorded from the corona discharge of precursor p-chloro-ethylbenzene seeded in a large amount of inert carrier gas helium using a pinhole-type glass nozzle coupled with a technique of corona excited supersonic expansion. From the comparison with the vibronic spectrum of the p-chlorobenzyl radical, we identified the evidence of formation of the jet-cooled p-chloro-<TEX>${\alpha}$</TEX>-methylbenzyl radical in the corona discharge of precursor p-chloro-ethylbenzene.

Spectroscopic identification of benzyl-type radicals generated by corona discharge of 2-chloro-4-fluorotoluene

By means of a technique of corona excited supersonic expansion coupled with a pinhole-type glass nozzle, we generated vibronically excited but jet-cooled benzyl-type radicals from precursor 2-chloro-4-fluorotoluene seeded in a large amount of inert carrier gas He. From an analysis of the visible vibronic emission spectrum, we found evidence of the formation of the 2-chloro-4-fluorobenzyl and 4-fluorobenzyl radicals. A possible pathway for the formation of these benzyl-type radicals is herein proposed. Also, the electronic energy in the D(1) → D(0) transition and the vibrational mode frequencies of the 2-chloro-4-fluorobenzyl radical in the ground electronic state were accurately determined, for the first time, by comparison with ab initio calculations and the known vibrational data of the precursor.

Spectroscopic observation of jet-cooled 2-fluoro-m-xylyl radical

The jet-cooled 2-fluoro-m-xylyl radical was generated and vibronically excited in a corona excited supersonic expansion from precursor 2-fluoro-m-xylene seeded in a large amount of carrier gas helium. The well-resolved visible vibronic emission spectrum of the jet-cooled 2-fluoro-m-xylyl radical was recorded using a long-path monochromator. From the analysis of the spectrum, we determine an accurate electronic energy of the D(1) → D(0) transition and the frequencies of vibrational modes in the ground electronic state by comparison with those of ab initio calculations and the known spectroscopic data of 2-fluoro-m-xylene for the first time.

Confirmed assignments of isomeric dimethylbenzyl radicals generated by corona discharge

The controversial vibronic assignments of isomeric dimethylbenzyl radicals were clearly resolved by using different precursors. By employing corresponding dimethylbenzyl chlorides as precursors, we identified the origins of the vibronic bands of the dimethylbenzyl radicals generated by corona discharge of 1,2,4-trimethylbenzene. From the analysis of the spectra observed from the dimethylbenzyl chlorides in a corona excited supersonic expansion, we revised previous assignments of the 3,4-, 2,4-, and 2,5-dimethylbenzyl radicals. Spectroscopic data of electronic transition and vibrational mode frequencies in the ground electronic state of each isomer were accurately determined by comparing them with those obtained by an ab initio calculation and with the known vibrational data of 1,2,4-trimethylbenzene.

Alkyl Group Dissociation During Corona Excitation of Alkylbenzenes

Well-resolved vibronic emission spectra were recorded in the visible region from the corona discharge of precursor alkylbenzenes in a technique of corona excited supersonic expansion using a pinhole-type glass nozzle. From the observed spectra, we found the evidence of the presence of benzyl-type radicals generated by dissociation of C-C or C-H bonds of alkyl group. After identification of benzyl-type radicals formed in the corona discharge, we suggest that energy densities in alkyl chain play a crucial role in determining the bond dissociation during corona excitation.

Isomeric Trimethylbenzyl Radicals Produced by Corona Discharge of 1,2,3,5-Tetramethylbenzene

Isomeric trimethylbenzyl radicals were generated and vibronically excited from precursor 1,2,3,5-tetramethylbenzene, isodurene, with a large amount inert carrier gas helium in a corona excited supersonic expansion (CESE) using a pinhole-type glass nozzle. A long-path monochromator was used to record the visible vibronic emission spectra of the jet-cooled benzyl-type radicals in the electronic transition. From the analysis of the spectra, we identified the evidence of the presence of three isomeric trimethylbenzyl radicals in the corona discharge, and obtained the electronic energy and a few vibrational mode frequencies in the ground electronic state for each isomer.