VUV photochemistry and nuclear spin conversion of water and water–orthohydrogen complexes in parahydrogen crystals at 4 K

Abstract

Samples of H2O, HDO, and D2O were isolated in solid parahydrogen (pH2) matrices and irradiated by vacuum ultraviolet (VUV) radiation at 147 nm. Fourier-Transform Infrared (FTIR) spectra showed a clear...

Formation of Para-H2O by Vacuum-UV Photolysis of O2 in Solid Hydrogen: Implication for Astrochemistry

“…The IR absorption spectra of the O 2 / n H 2 matrix samples in the 3200–3800 cm –1 spectral region recorded from the same experiments are presented in Figure A,B; the absorption lines of the ν 1 and ν 3 modes associated with nonrotating H 2 O–( o H 2 ) n are observed at 3644.5 and 3736.3 cm –1 (marked C1), respectively. Lines observed at 1632.1, 3758.0, and 3765.0 cm –1 are clearly associated with H 2 O, but they were not reported previously for H 2 O in an n H 2 matrix. , These line positions are similar to those reported for the ro-vibrational transitions of p H 2 O in solid rare-gas matrices − and solid p H 2 ; − p H 2 O is thus a most likely carrier of these lines. A similar photolysis experiment was hence performed in solid p H 2 (containing ∼2% o H 2 ) for comparison; the corresponding IR spectra are shown in Figures C and C.…”

“…Besides H 2 O, products were readily identified on the basis of the expected photochemical models 1,31 and reported IR features. 24,25,31 HO 2 was formed under all experimental conditions because of the absence of an energy barrier for the reaction O 2 + H → HO 2 (ref 3); H was produced from O + H 2 → H + OH. O 3 was observed upon photolysis with broadband VUV light but not from photolysis at 121.6 nm light; instead, O 3…”

“…The NSC of water in space is thus proposed to occur in condensed phases. In the recent two decades, the NSC of water as bulk ice ,, or embedded in solid matrices − or confined inside nanostructured materials − has been extensively examined experimentally and theoretically.…”

“…As the number of clustering o H 2 is reduced to one or zero, H 2 O starts to rotate. The absence of isolated o H 2 O upon photolysis in n H 2 might be due to strong interactions between o H 2 and o H 2 O, which result in the rapid formation of H 2 O–( o H 2 ) n clusters in the initial period. , …”

Hydrocarboxyl Radical as a Product of α-Alanine Ultraviolet Photolysis

“…Because the cisconformer was only observed in fully deuterated experiments, this additional CO 2 production may reflect the nature of the ground-state HOCO potential surface, where the cis-conformer tends to dissociate to H + CO 2 . The concentration changes of H 2 O/HDO was similar to that of CO, which can be explained by the reactions of OH/OD produced from the OH/OD + CO dissociation channel with H 2 or H. 37 Additionally, the formation of formic acid may also be caused by the reaction between excited HOCO and surrounding H 2 .…”