Near-Infrared Laser Induced Conformational Change of Alanine in Low-Temperature Matrixes and the Tunneling Lifetime of Its Conformer VI

被引:59
作者
Bazso, Gabor [1 ]
Najbauer, Eszter E. [1 ]
Magyarfalvi, Gabor [1 ]
Tarczay, Gyoergy [1 ]
机构
[1] Eotvos Lorand Univ, Inst Chem, Lab Mol Spect, H-1518 Budapest 112, Hungary
基金
匈牙利科学研究基金会;
关键词
MOLECULAR-ORBITAL METHODS; ISOLATION FT-IR; MILLIMETER-WAVE SPECTROSCOPY; UV-INDUCED ISOMERIZATION; SUPERSONIC JET; AB-INITIO; GAS-PHASE; INDUCED PHOTOISOMERIZATION; ELECTRON-DIFFRACTION; INTERNAL-ROTATION;
D O I
10.1021/jp400196b
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The near- and mid-IR spectra of alpha-alanine isolated in low-temperature Ar, Kr, and N-2 matrixes were measured. Production of the short-lived conformer VI at the expense of the predominant conformer I was observed upon short irradiation with NIR laser light at the first O-H stretching overtone band of conformer I. Conformer VI decays by H-atom tunneling at 12 K with half-lives of 5.7 +/- 1 s, 2.8 +/- 1 s in Ar (two different sites), 7.0 +/- 1 s in Kr, and 2.8 x 10(3) +/- 1.2 x 10(3) s in N-2. Upon prolonged irradiation, conformer I slowly transformed into conformer ha. On the basis of these irradiation experiments, the unambiguous vibrational assignments of conformers I, IIa, and VI are given. In contrast to similar experiments for glycine, the irradiation experiments did not lead to the formation of conformer IIIb. This is explained by a very low IIIb -> I barrier height computed for alanine, which results in a very fast depletion of conformer IIIb even in low-temperature matrixes.
引用
收藏
页码:1952 / 1962
页数:11
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