Luminescence infrarouge des gaz excités par l'azote activé i. oxyde de carbone

Emission spectra of carbon monoxide excited by nitrogen activated by high frequency discharge have been recorded near 4.7 μ. Analysis of these spectra allowed us to show the vibrational transitions 1 → 0, 2 → 1, 3 → 2, 4 → 3 and to define a rotational temperature of the order of 430 °K and a vibrational temperature of about 4 600 °K. The maximum partial pressure obtained for excited CO has been estimated of 0.30 torr. The mechanism of the excitation is discussed and the most probable hypothesis is a transfer of the energy of the vibrationally excited nitrogen molecules in the fundamental electronic state, according to the reaction : N≠2 + CO ↔ N2 + CO -. Within this hypothesis, one must infer that 10-2 s after the discharge about 85 % of the activated nitrogen molecules are distributed on the vibrational levels following a Boltzmann equilibrium defining a temperature of 4 600 °K. An attempt has been made to estimate the de-excitation constant of CO by the walls.Des spectres d'émission de l'oxyde de carbone excité par l'azote activé par haute fréquence ont été enregistrés vers 4,7 μ. L'analyse de ces spectres a permis de mettre en évidence les transitions vibrationnelles 1-0, 2-1, 3-2, 4-3 et de définir une température de rotation d'environ 430 °K et une température de vibration de l'ordre de 4 600 °K. La pression partielle maximum obtenue pour CO excité a été estimée à 0,30 torr. Le mécanisme de l'excitation est discuté et l'hypothèse considérée comme la plus probable est un transfert de l'énergie des molécules d'azote vibrationnellement excitées dans l'état électronique fondamental, suivant le schéma N≠2 + CO ↔ N2 + CO≠. Dans cette hypothèse on doit conclure que 10-2 s après la décharge environ 85 % des molécules de l'azote activé sont réparties sur les niveaux vibrationnels suivant un équilibre de Boltzmann définissant une température de 4 600 °K. Une tentative d'estimation de la constante de désexcitation de CO par les parois a été faite

Relaxations vibrationnelle et rotationnelle dans un laser a CO-N2

A double resonance method inside the optical cavity of a CO-N2 laser has been used to study vibrational and rotational relaxation processes in the amplifying medium. Measurements of rotational relaxation of CO are in agreement with other authors and support the ΔJ = ± 1 selection rules for the collisional processes. Measurements of the V-V exchange rates between two molecules in a high vibrational state (v ≃ 10) suggest higher values than those calculated by the Schwartz-Slawsky-Herzfeld and Sharma-Brau theories from measurements carried out on the low vibrational levels.Une méthode de double résonance à l'intérieur de la cavité optique d'un laser à CO-N2 a été utilisée dans le but de suivre les processus de relaxations vibrationnelle et rotationnelle dans le milieu amplificateur. Les mesures de relaxation rotationnelle de CO donnent des résultats en accord avec d'autres auteurs et sont en faveur de la règle de sélection Δ J = ± 1 pour les transferts collisionnels. Les mesures des vitesses d'échange V- Ventre deux molécules de CO portées sur des hauts niveaux de vibration (v ≃ 10) indiquent des valeurs plus grandes que celles calculées par les théories de Schwartz-Slawsky-Herzfeld et de Sharma-Brau à partir des mesures faites sur les bas niveaux

Intramolecular electronic-to-vibrational energy conversion in NO trapped in Xe matrices

Energy- and time-resolved IR emission spectra of NO trapped in Kr and Xe matrixes following excitation by an ArF laser were recorded. In Kr matrixes, the ground-state levels are predominantly populated by radiative decay from the a 4P state. The Xe matrixes ground-state v - v - 2 IR emission bands were obsd. for v = 22-3, confirming that in the NO/Xe system most of the excited-state energy is dissipated nonradiatively into the ground state. The IR bands show typical radiative decay times in the ms range but in Xe for all measured levels (v = 22-15), the rise time is ?1 ms. The nonradiative decay of the excited states to the ground state of NO in Xe matrixes is highly nonresonant. [on SciFinder (R)

Spectroscopy and photodissociation of dimethylzinc in solid argon. 2. FTIR detection ArF laser photolysis

The IR spectroscopy of matrix-isolated DMZ is presented as a precursor for the analysis of DMZ photochemistry in the solid rare gases. In agreement with gas-phase work, the present study reassigns the band observed at 1309.2 cm-1, currently assigned in the matrix literature to the bending mode of the impurity methane, to the ν10 + ν14 band combination mode of DMZ. From a combination of IR absorption and UV luminescence studies, atomic zinc and a pair of methyl radicals (Zn + 2CH3) are identified as the photochemical products formed with ArF excimer laser photolysis. A concerted dissociation pathway of DMZ in solid Ar is considered to be the only mechanism leading to the production of methyl radicals in the vicinity of ground-state atomic zinc. The lack of observation of the methylzinc (CH3Zn) and methyl radicals as products is explained in terms of the rapid geminate recombination of these radicals in the matrix cage, which in turn explains the poor efficiency of DMZ dissociation in the solid. Evidence exists for the formation of secondary products with ArF photolysis, namely, the production of ethylzinc hydride and acetylene. It is proposed that the former arises from the excited-state insertion of atomic zinc into the C−H bonds of the small amounts of ethane arising from the recombination of the methyl radicals. Acetylene is a product of ArF dissociation of ethylene which results from recombination of hot methyl radicals

Photodissociation of Dimethylmercury in Argon Matrixes by 193 and 248 nm Laser Irradiation

The photodissociation of dimethylmercury, Hg(CH3)2, in dilute argon matrixes is induced efficiently by ArF (193 nm) and inefficiently by KrF (248 nm) laser irradiation. The reaction products are identified by their IR absorption and UV absorption and luminescence spectra. Upon ArF photolysis, ethane remaining in close proximity of a Hg atom (Hg‚C2H6) is the main reaction product. The Hg‚C2H6 complex is destroyed by KrF radiation with formation of HHgC2H5, which is photolyzed, giving HgH2 and ethylene. Unidentified near UV emission bands recorded during irradiation are tentatively assigned to an unstable Hg‚CH3 complex