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ArF-laser-induced emission from NO(B2Π,ν′=7) and O2(B3Σ−u,ν′=4)
166 ArF-laser-induced emission f&m NO(B 217,v’ = 7) and 02(B 3ZU-,v’ = 4) KAZUNIKO
SHIBUYA*
and F. STUHL
Physikdische Chemie I, Ruhr-Vniversitit Bochum, Postfach 102148, D-4630
Bochum (F.R.G.)
NO and O2 were excited by a 193 nm ArF excimer laser to prepare electronically excited NO(B 217,v’ = 7) and 02(B 3ZU-,u’ = 4) respectively. Single vibronic emission of the fi(7,v”) progression was dominantly observed at low pressures of NO (about 0.1 Torr). The addition of argon (0.1 - 10 Torr) quenched the /3(7,~“) bands and enhanced the d(O,v”) and y(3,v”) bands. This behaviour is directly related to the predissociation mechanism of NO, since the B 2Z7(v’ = 7), C ‘I~(v’ = 0) and A ‘Z’(v’ = 3) states lie at the dissociation limit. Furthermore, selective single vibronic excitation of 0&3,v = 4) was performed for the first time; the lifetime of this state was estimated to be between 10-” and lo-l2 s. The effect of colIisions on the corresponding fluorescence is presented. This work was supported by Grant DFG-SF.B
* Permanent
address: Department
Laser-inducedfluorescence level G. DORNHUFER,
W. HACK
of Chemistry,
42-80.
Tokyo Institute of Technology,
Tokyo, Japan.
of CF,(A lB1) after excitation of a single vibronic
and W. LANGEL
Max- Planck- Institutfiir Striimungsforschung, Biittingerstrasse4 - 8, D-3400
Gettingen (F-R. G.)
The fluorescence spectrum of CF,(.& ‘B1(O, 6, 0)) was observed with high spectral and time resolution. The excitation of ground state CF2 (x ‘Ai) to the single vibronic level (0, 6, 0) of the first electronic excited state was performed with a KrF excimer laser at 248 nm. The collision-free lifetime of CF,(A ‘B1) was determined to be 55 ns. The quenching rate constants with various molecules were determined and the quenching mechanisms are discussed with respect to electronic and vibrational deactivation. The vibrational deactivation in the upper states proceeds via (0, 5, 0) and (1, 3, 0) levels. The (1, 3, 0) vibrational state is populated from the (1, 4, 0) level which is shown to be populated with a very high rate by collision. The evolution from the population of primarily excited high rotational states to a room temperature thermal rotational distribution was observed and is described quantitatively.
SHIBUYA*
and F. STUHL
Physikdische Chemie I, Ruhr-Vniversitit Bochum, Postfach 102148, D-4630
Bochum (F.R.G.)
NO and O2 were excited by a 193 nm ArF excimer laser to prepare electronically excited NO(B 217,v’ = 7) and 02(B 3ZU-,u’ = 4) respectively. Single vibronic emission of the fi(7,v”) progression was dominantly observed at low pressures of NO (about 0.1 Torr). The addition of argon (0.1 - 10 Torr) quenched the /3(7,~“) bands and enhanced the d(O,v”) and y(3,v”) bands. This behaviour is directly related to the predissociation mechanism of NO, since the B 2Z7(v’ = 7), C ‘I~(v’ = 0) and A ‘Z’(v’ = 3) states lie at the dissociation limit. Furthermore, selective single vibronic excitation of 0&3,v = 4) was performed for the first time; the lifetime of this state was estimated to be between 10-” and lo-l2 s. The effect of colIisions on the corresponding fluorescence is presented. This work was supported by Grant DFG-SF.B
* Permanent
address: Department
Laser-inducedfluorescence level G. DORNHUFER,
W. HACK
of Chemistry,
42-80.
Tokyo Institute of Technology,
Tokyo, Japan.
of CF,(A lB1) after excitation of a single vibronic
and W. LANGEL
Max- Planck- Institutfiir Striimungsforschung, Biittingerstrasse4 - 8, D-3400
Gettingen (F-R. G.)
The fluorescence spectrum of CF,(.& ‘B1(O, 6, 0)) was observed with high spectral and time resolution. The excitation of ground state CF2 (x ‘Ai) to the single vibronic level (0, 6, 0) of the first electronic excited state was performed with a KrF excimer laser at 248 nm. The collision-free lifetime of CF,(A ‘B1) was determined to be 55 ns. The quenching rate constants with various molecules were determined and the quenching mechanisms are discussed with respect to electronic and vibrational deactivation. The vibrational deactivation in the upper states proceeds via (0, 5, 0) and (1, 3, 0) levels. The (1, 3, 0) vibrational state is populated from the (1, 4, 0) level which is shown to be populated with a very high rate by collision. The evolution from the population of primarily excited high rotational states to a room temperature thermal rotational distribution was observed and is described quantitatively.