The vibration–rotation of H2O and its complexation with CO2 in solid argon revisited

Abstract

Fourier-transform infrared spectroscopy in the frequency range 400-4000 cm -1 has been used to investigate the absorption of H 2 O and H 2 O:CO 2 complex isolated in solid argon. Thanks to the lowest temperature reached in our experiment, temperature effects and nuclear spin conversion studies allow us to propose a new assignment of the rovibrational lines in the bending band n 2 for the quasi-freely rotating H 2 O. An additional wide structure observed in this band shows two maxima around 1657.4 and 1661.3 cm -1 , with nuclear spin conversion of the high frequency part into the low frequency one. This structure is tentatively attributed to a rotation-translation coupling of the molecule in the cage. However, the equivalent effect is not observed in the vibrational stretching bands n 1 and n 3 . Finally, by double doping experiments with CO 2 , important new structures appear, leading us to unambiguously extract the frequencies of the lines of the H 2 O:CO 2 complex.

Infrared spectra of the water-nitrogen complexes (H2O)2–(N2)n(n=1–4) in argon matrices

“…Most of the observed lines inFig. 1͑a͒are assigned to the H 2 O monomer; the relative intensities between the monomer lines agree with those reported at 20 and 30 K 12,13. In addition, the five features of the H 2 O dimer at 3707.5, 3573.6, 3632.9, 1611.0, and 1593.2 cm −1 are observed, which correspond to the free and bonded OH stretches of the PD, the 1 stretch of the PA, and 2 bends of the PD and PA, respectively.…”

“…3,[5][6][7][8][9][10][11][12][13] For the H 2 O dimer, four absorption lines corresponding to the OH stretching vibrations were assigned in the previous studies 9-12 to the 1 symmetric and 3 asymmetric stretches of the PA and PD molecules. The two OH stretching modes of the PD molecules, however, should be denoted as the "free" and "bonded" OH stretches.…”

Fast Nuclear Spin Conversion in Water Clusters and Ices: A Matrix Isolation Study

“…19,27 However, this frequency coincides with a known band of H 2 O-CO 2 complexes. 17 Overall, we did not detect any additional bands that could be assigned to nonrotating water molecules in the ν 1 and ν 3 ranges of the spectra. Finally, a relatively intense and broad structure (10 cm À1 ) at ∼1660 cm À1 was assigned to rotation-translation satellites of the 1 11 r 0 00 line.…”

“…The band positions are in good agreement with previous Ar matrix studies. 17,19,23,25 Our recent He droplet study 32 gives the positions of the BD, SA, and FD bands to be 3597.4, 3654.2, and 3729.5 cm À1 , respectively, that is, having ∼22 cm À1 blue shift with respect to corresponding frequencies in Ar matrix. The relative intensities of the dimer bands are in good agreement with those obtained in our He droplet study.…”

Chemistry in low-temperature matrices

“…The vibration-rotation of H 2 O and its complexation with CO 2 in solid argon has been revisited. 26 The new work here involves the possibility of reaching lower matrix temperatures than had previously been achieved. This allows a new assignment to be made for the rotational lines in the bending mode of the quasi-rotating H 2 O moiety.…”