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Irradiation of dilute mixtures of NH.sub.3] and O2 dispersed in solid Ne at 3.6 K with light of wavelengths 200,192.5, 173, and 143 nm from a synchrotron initiated photochemical dissociation of those precursors and the production of N, NH, [NH.sub.2], O, [O.sub.3], [HO.sub.2], NO, N[O.sub.2], [N.sub.2]O, [H.sub.2]O, HONO in both s-cisoid and s-transoid rotational isomers, and HON[O.sub.2], detected according to their spectra in mid-infrared absorption from 450 to 4000 [cm.sup.-1] and in absorption and emission from 200 to 1100 nm. Key words: mid-infrared absorption spectra, visible emission spectra, visible absorption spectra, photochemistry, far-ultraviolet excitation. L'irradiation de mélanges dilués de [NH.sub.3] et d'[O.sub.2] dispersés dans le Ne solide à 3,6 K par une lumière synchrotron de longueurs d'onde de 200,192,5,173 et 143 nm a entraîné la dissociation photochimique de ces précurseurs et la formation des espèces N, NH, [NH.sub.2], O, [O.sub.3], [HO.sub.2], NO, N[O.sub.2], [N.sub.2]O, [H.sub.2]O et HONO sous les deux formes d'isomères rotationnels, scisoïde et stransoïde, ainsi que HON[O.sub.2]. Ces espèces ont été détectées selon leur spectre d'absorption dans l'infrarouge moyen de 450 à 4000 [cm.sup.-1] et leurs spectres d'absorption et d'émission de 200 à 1100 nm. [Traduit par la Rédaction] Mots-clés : spectres d'absorption dans l'infrarouge moyen, spectres d'émission dans le visible, spectres d'absorption dans le visible, photochimie, excitation dans l'ultraviolet lointain., Introduction Many reports have appeared on the production of novel species by means of the photochemical decomposition of a suitable precursor dispersed in an inert diluent at temperatures less than [...]

The infrared (IR) spectrum of monobridged Si2H4 (denoted as mbr-Si2H4) isolated in solid Ar was recorded, and a set of lines (in the major matrix site) observed at 858.3 cm−1, 971.5 cm−1, 999.2 cm−1, 1572.7 cm−1, 2017.7 cm−1, 2150.4 cm−1, and 2158.4 cm−1 were characterized. The species was produced by the electron bombardment of an Ar matrix sample containing a small proportion of SiH4 during matrix deposition. Upon photolysis of the matrix samples using 365 nm and 160 nm light, the content of mbr-Si2H4 increased. The band positions, relative intensity ratios, and D-isotopic shift ratios of the observed IR features are generally in good agreement with those predicted by the B3LYP/aug-cc-pVTZ method. In addition, the photochemistry of the observed products was discussed. [ABSTRACT FROM AUTHOR]

Phenoxide anions (PhO−) and phenoxy radicals (PhO) were generated by the electron bombardment of a phenol/argon sample during matrix deposition. Further irradiation of the matrix sample at 365 nm led to the detachment of the electron from PhO− and afforded its neutral counterpart PhO in solid Ar. In a separate experiment, the photolysis of a phenol/Ar matrix at 160 nm mainly afforded PhO, phenyl (Ph) radicals, and various open‐chain ketenes, but no PhO−. The Infrared (IR) lines of PhO− were assigned on the basis of the observed photochemical behaviors and the prediction of the vibrational wavenumbers with the corresponding IR intensities predicted by the B3LYP/aug‐cc‐pVTZ theory. [ABSTRACT FROM AUTHOR]

The absorption spectrum of solid acetylene (C2H2) at 10 K was measured in wavelength range 107–250 nm with UV light from a synchrotron source. Based on the absorption spectrum, we irradiated at 175 nm the icy acetylene at 60 K; the results yielded a new set of IR absorption lines with similar temporal profiles of production during the photolysis periods. From icy 12C2H2, these new features were recorded at 3276.8, 1598.7, 963.0, 936.3, and 671.3 cm−1, which are assigned to modes ν1, ν6, ν14, ν15, and ν11 (mixing with ν17), respectively, of vinylacetylene (C4H4) based on the results of 13C- and D-isotopic experiments and quantum-chemical calculations. These calculations using density-functional theory (B3LYP/6–311++G**) predict vibrational wavenumbers and IR intensities of vinylacetylene that agree satisfactorily with our experimental results. This work enhances our understanding of the photochemistry of icy acetylene in cold astronomical environments; for instance, the present result can be applied directly to the photochemical processes on Titan's surface. [ABSTRACT FROM AUTHOR]

During photoexcitation of icy N2 at 121.6 nm from a synchrotron source, emission lines in the vibronic progression of the Vegard–Kaplan system, A , for N2 were concurrently observed in the wavelength range 210–430 nm; emission lines of N (2P → 2D) and N (2D → 4S) were recorded in the wavelength range 460–1100 nm. After irradiation of icy N2 at 121.6 nm, the characteristic infrared absorption lines of N3 radical in vibrational mode ν3 appeared at 1652.6 and 1657.8 cm−1. When the irradiated icy sample containing N3 radical was subsequently subjected to photolysis at 190 nm, only emission from N (2D → 4S) was concurrently recorded; the IR absorption lines of N3 vanished. The result indicates that N3 radical in icy N2 can be dissociated into the N (2D) atom and N2 () molecule with light at 190 nm. Our work thus has ramifications for nitrogen transformation in cold astrophysical environments. [ABSTRACT FROM AUTHOR]