CN photodissociation and predissociation chemical lasers: Molecular electronic and vibrational laser emissions
Abstract
Molecular electronic [CN*(A2Π3/2, v' = 0) → CN(X2Σ+, v″ = 0,1,2)] and vibrational [CN† (X2Σ+, v') → CN(X2Σ+, v' - 1), v' = 5,4,3,2] cyanide radical laser emissions have been observed following photodissociative and predissociative fragmentation of cyanide parents [HCN, ClCN, BrCN ICN, (CN)2, CH3NC, CF3CN, C2F5CN] at λ ≥ 1550 Å. The observed transitions and their relative gain coefficients and quenching behaviors are used in connection with spectroscopy and fluorescence experiments to formulate a state-to-state photochemical reaction mechanism, viz.,
RCN lim →ℏ ωR+CN*(A2Πi,v'=0primarily), CN*(A2Πi,v'=0)+M→ CN†(X2Σ+,v″=4 primarily)+M, in which nascent photochemical products are formed with high electronic population inversion [NCN*(A)/NCN(X) ≫ 1] and no vibronic inversion within the A2Πi manifolds (i.e., v = 0 is the principal product vibronic state). Near-resonant collision-induced intersystem crossing is shown to preferentially populate v = 4 within the X2Σ+ electronic manifold. Electronic and vibronic population inversions are treated via state-to-state adiabatic correlation diagrams and a simple dynamical model for reaction product vibronic state distributions. Anomalous laser behavior in the BrCN photodissociation system is rationalized via an intramolecular near-resonant E → E' energy transfer scheme.- Publication:
-
Journal of Chemical Physics
- Pub Date:
- December 1974
- DOI:
- 10.1063/1.1681793
- Bibcode:
- 1974JChPh..61.4700W
- Keywords:
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- Chemical Lasers;
- Cyanides;
- Free Radicals;
- Laser Outputs;
- Molecular Oscillations;
- Photodissociation;
- Absorption Spectra;
- Fluorescence;
- Molecular Electronics;
- Molecular Excitation;
- Photolysis;
- Population Inversion;
- Spectroscopy;
- Tables (Data);
- Ultraviolet Spectra;
- Lasers and Masers