| Autor: |
Läuter, Almuth, Suresh, Dhanya, Volpp, Hans-Robert |
| Předmět: |
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| Zdroj: |
Journal of Chemical Physics; 4/1/2003, Vol. 118 Issue 13, p5821, 10p, 1 Chart, 3 Graphs |
| Abstrakt: |
The dynamics of chlorine and hydrogen atom formation in the 193.3 nm gas-phase laser photolysis of room-temperature 1,1-dichloro-1-fluoroethane, CH[sub 3] CFC1[sub 2] (HCFC- 14 lb), were studied by means of the pulsed-laser-photolysis and laser-induced fluorescence (LIF) "pump-and-probe" technique. Nascent ground-state C1(²P[sub 3/2]) and spin-orbit excited C1[sup *](²p[sub 1/2]) as well as H(²S) atom photofragments were detected under collision-free conditions by pulsed Doppler-resolved laser-induced fluorescence measurements employing narrow-band vacuum ultraviolet probe laser radiation, generated via resonant third-order sum-difference frequency conversion of dye laser radiation in krypton. Using HC1 photolysis as a reference source of well-defined C1(²P[sub 3/2]), C1[sup *](2P[sub 1/2]), and H atom concentrations, values for the chlorine-atom spin-orbit branching ratio [Cl[sup *]]/[C1] = 0.36 ± 0.08, the total chlorine atom quantum yield (φ[sub Cl + Cl[sup *]]) = 1.01 ± 0.14), and the H atom quantum yield (φ[sub H] 0.04± 0.01) were determined by means of a photolytic calibration method. From the measured C1 and Cl[sup *] atom Doppler profiles the mean relative translational energy of the chlorine fragments could be determined to be E[sub T(Cl)]= 157± 12 kJ/mol and E[sub T(Cl[sup *]]) 165 ± 12 kJ/mol. The corresponding average values 0.56 and 0.62 of the fraction of total available energy channeled into CH[sub 3] CFCl + C1/CI[sup *] product translational energy were found to lie between the limiting values 0.36 and 0.85 predicted by a soft impulsive and a rigid rotor model of the CH[sub 3] CFC1[sub 2]→ CH[sub 3] CFC1 + C1/Cl[sup *] dissociation processes, respectively. The measured total chlorine atom quantum yield along with the rather small H atom quantum yield as well as the observed energy disposal indicates that direct C-C1 bond cleavage is the most important primary fragmentation... [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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