Nuclear spin conversion of O2 doped solid normal H2 at 4.2 K: an empirical law to determine the ortho-H2 concentration by infrared absorption spectroscopy

International audienc

Infrared spectroscopy of solid normal hydrogen doped with CH3F and O2 at 4.2 K: CH3F:O2 complex and CH3F migration

International audienc

Infrared spectroscopy of solid normal hydrogen doped with CH₃F and O₂ at 4.2 K: CH₃F:O₂ complex and CH₃F migration

Double doping of solid normal hydrogen with CH₃F and O₂ at about 4.2 K gives evidence of (ortho-H₂)n:CH₃F clusters and of O₂:CH₃F complex formation. A FTIR analysis of the time evolution of the spectra, in the ν₃ C–F stretching mode region, points out a behavior of the clusters very different from that of (ortho-H₂)n:H₂O clusters. The main point is the observation of CH₃F molecules migration in solid para-H₂ at 4.2 K, which is a behavior different from H₂O in identical experimental conditions. This is proved by the increase with time of the CH₃F:O₂ complex integrated intensity with a rate constant K=2.7(2) ⋅10⁻⁴s⁻¹

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

Fourier-transform infrared spectroscopy in the frequency range 400–4000 cm–¹ has been used to investigate the absorption of H₂O and H₂O:CO₂ 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 n₂ for the quasi-freely rotating H₂O. 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-ranslation coupling of the molecule in the cage. However, the equivalent effect is not observed in the vibrational stretching bands n₁ and n₃. Finally, by double doping experiments with CO₂, important new structures appear, leading us to unambiguously extract the frequencies of the lines of the H₂O:CO₂ complex

nuclear spin conversion of H2O trapped in solid xenon at 4.2K: a new assignment of v2 rovibrational lines

International audienc

Nuclear spin conversion of water diluted in solid argon at 4.2 K: Environment and atmospheric impurities effects

International audienc