Bimolecular gas-phase processes with the participation of vibrationally excited triplet molecules of aromatic ketones

1999 ◽  
Vol 66 (1) ◽  
pp. 76-80
Author(s):  
G. A. Zalesskaya ◽  
D. I. Baranovskii ◽  
E. G. Sambor
Keyword(s):  
Gas Phase ◽  
Vibrationally Excited ◽  
Excited Triplet ◽  
Aromatic Ketones

The Dielectric Discharge as an Efficient Generator of Active Nitrogen for Chemiluminescence and Analysis

1983 ◽  
Vol 37 (6) ◽  
pp. 545-552 ◽  
Author(s):  
John Kishman ◽  
Eric Barish ◽  
Ralph Allen
Keyword(s):  
Gas Phase ◽  
Ground State ◽  
Band System ◽  
Electrothermal Atomization ◽  
Characteristic Radiation ◽  
Gaseous Species ◽  
Vibrationally Excited ◽  
Active Nitrogen ◽  
Excited Species ◽  
Intense Emission

A predominantly blue “active nitrogen” afterglow was generated in pure flowing nitrogen or in air by using a dielectric discharge at pressures from 1 to 20 Torr. The afterglow contains triplet state molecules and vibrationally excited ground state molecules. These species are produced directly by electron impact without the formation and recombination of nitrogen atoms. The most intense emission is the N2 second positive band system. The N2 first positive and N2+ first negative systems are also observed. The spectral and electrical properties of this discharge are discussed in order to establish guidelines for the analytical use of the afterglow for chemiluminescence reactions. The metastatic nitrogen efficiently transfers its energy to atomic and molecular species which are introduced into the gas phase and these excited species emit characteristic radiation. The effects of electrothermal atomization of Zn and the introduction of gaseous species (e.g., NO) on the afterglow are described.

Spectrofluorometric studies. VIII. The effect of CO2 and CHCl3 on the photochemistry of monofluorobenzene

1970 ◽  
Vol 48 (10) ◽  
pp. 1607-1613 ◽  
Author(s):  
M. E. MacBeath ◽  
I. Unger
Keyword(s):  
Quantum Yield ◽  
Quantum Yields ◽  
Vibrationally Excited ◽  
Excited Triplet ◽  
Improved Technique ◽  
Triplet Quantum Yields

The sensitized emission of biacetyl technique was used to study the effect of CHCl3 and CO2 on the triplet quantum yields of both benzene and monofluorobenzene.The monofluorobenzene was studied at λ excitation (λex) of 2470, 2590, and 2670 Å. At 2470 Å, the triplet yield increased by over 40% with both added gases; at λex 2590 Å, by around 30%; and at λex 2670 Å, about 20%. CHCl3 is slightly more effective than CO2 in enhancing the biacetyl phosphorescent yield. The quantum yield of fluorescence was unchanged with these added gases. Using a slightly improved technique, the comparison irradiation of a benzene–biacetyl mixture at λex 2540 Å with added CHCl3 was repeated. The results confirmed that the biacetyl phosphorescent yield decreased with increasing pressures of CHCl3, but suggest that the effect is not as great as previously reported. At the same wavelength, the triplet yield is unaffected by the addition of CO2. The quantum yield of fluorescence of benzene is virtually unaffected by the added gases. The data suggest that in the monofluorobenzene case the CO2 and CHCl3 are quenching vibrationally excited triplet fluorobenzene molecules.

Etude à basse température dans l'infrarouge proche du dimère (NO)2

1984 ◽  
Vol 62 (4) ◽  
pp. 322-329 ◽  
Author(s):  
V. Menoux ◽  
R. Le Doucen ◽  
C. Haeusler ◽  
J. C. Deroche
Keyword(s):  
Excited State ◽  
Gas Phase ◽  
Ground State ◽  
Near Infrared ◽  
Heat Of Formation ◽  
Wave Number ◽  
Vibrational Modes ◽  
Vibrationally Excited ◽  
Rotational Constants ◽  
Absorption Intensity

The spectrum of the dimer (NO)2 in the gas phase has been studied in the near infrared at temperatures between 118 and 138 K. More specifically, the measure of absorption intensity of the ν4 and ν1 + ν4 bands has yielded the heat of formation of the dimer, −2.25 kcal/mol at 128 K, and revealed the influence of the low vibrational modes on this measure. The observation of the ν4 – ν6, difference band has yielded the wave number value of the ν6, fundamental band, forbidden in the infrared. The rotational constants of the vibrationally excited state were found to be larger than the ground state rotational constants, this result being very unusual.

The thermal and photochemical decomposition of maleic anhydride in the gas phase

1981 ◽  
Vol 59 (9) ◽  
pp. 1342-1346 ◽  
Author(s):  
R. A. Back ◽  
J. M. Parsons
Keyword(s):  
Maleic Anhydride ◽  
Gas Phase ◽  
Light Emission ◽  
Order Rate Constant ◽  
Static System ◽  
Collisional Quenching ◽  
Vibrationally Excited ◽  
Concerted Mechanism ◽  
Photochemical Decomposition ◽  
Weak Light

The thermal decomposition of maleic anhydride has been studied in the gas phase in a static system at temperatures from 645 to 760 K and pressures from 0.7 to 20 Torr. The first-order rate constant for the homogeneous unimolecular reaction,[Formula: see text]is described by the Arrhenius parameters log A (s−1) = 14.33 (±0.3), and E = 60.9 (± 1) kcal/mol. The reaction appears to proceed through a concerted mechanism rather than a biradical one.The photochemical decomposition, studied at wavelengths from 220 to 350 nm, yielded the same products. At 300 nm and below, the decomposition was unaffected by pressure, but at longer wavelengths collisional quenching was observed. Weak light emission was observed on excitation between 350 and 380 nm. The absorption spectrum was measured from 250 to 400 nm, and three overlapping transitions, π*←π, π*←n+, and π*←n−, can be distinguished. The mechanism of the photolysis is discussed and it is concluded that it probably proceeds through internal conversion to a vibrationally excited ground state.

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