Local formation of HArF in solid argon: Low-temperature limit and thermal activation

Abstract

The H + Ar+ F reaction leading to HArF formation in an argon matrix is studied at temperatures down to 8 K. The effects of the precursor concentration, deuteration, IR light, and deposition temperature as well as thermal activation of this reaction are studied. It is found that HArF molecules are formed slowly but efficiently at 8 K in a photolyzed HF / Ar matrix, supporting the previously reported results. The formation rate of HArF ͑and DArF͒ exhibits a low-temperature limit and enhances at elevated temperatures with activation energy of about 40 meV. All the data show that HArF is formed as a result of a local reaction of hydrogen atoms with the parent Ar-F centers and the tunneling mechanism is very probable here. The locality of the precursor photolysis required for this tunneling reaction is consistent with the partial HArF formation observed during photolysis of HF in an argon matrix. The decay mechanism of ͑ArHAr͒ + cations is also studied. The present results confirm the previous conclusions that the decay of the cations is not essential to HArF formation.

Light induced reactions in cryogenic matrices

“…This subject has been reviewed recently by Nemukhin et al 21 and Khriachtchev, Ra¨sa¨nen and Gerber. 22 Lignell et al 61 studied the effects of the precursor concentration, deuteration, IR light, and deposition temperature as well as thermal activation on the H þ Ar þ F reaction leading to HArF formation in an argon matrix. They observed that HArF molecules formed slowly but efficiently at 8 K in a photolyzed HF/Ar matrix.…”

Theoretical study of HKrOX (X = F, Cl, Br and I): structure, anharmonic vibrational spectroscopy, stability and bonding

“…Previous researches showed that the noble-gas compounds HNgX (X represents a strongly electronegative species, such as a halogen, OH, CN or SH) are stabilized by strong Coulombic attraction within the HNg + and X À ion pair. 10,[44][45][46] To investigate the bonding character of HKrOX (X = F, Cl, Br and I), the Lo¨wdin population analyses of HKrOX (X = F, Cl, Br and I) have been carried out at the MP2 level, and the atomic partial charges are listed in Table 6. From Table 6 it is clear that the O and F atom charges are À0.513 and À0.242 in HKrOF, and the changes are À0.692 and À0.308 with respect to HOF, respectively.…”

Noble gases

“…9 The formation of HArF from the reaction of H + Ar + F in an argon matrix was studied at temperatures down to 8 K. The effects of the precursor concentration, deuteration, IR radiation, and deposition temperature as well as thermal activation on this reaction were studied, showing HArF is formed slowly, but efficiently, at 8 K, supporting previously reported results. 10 The 1 : 1 complexes of HY and HXeY (Y = Cl, Br) with N 2 in a Xe matrix were characterised by infrared spectroscopy. Small blue shifts (ca.…”