Neutralization of solvated protons and formation of noble-gas hydride molecules: Matrix-isolation indications of tunneling mechanisms?

Abstract

The ͑NgHNg͒ + cations ͑Ng= Ar and Kr͒ produced via the photolysis of HF / Ar, HF / Kr, and HBr/ Kr solid mixtures are studied, with emphasis on their decay mechanisms. The present experiments provide a large variety of parameters connected to this decay phenomenon, which allows us to reconsider various models for the decay of the ͑NgHNg͒ + cations in noble-gas matrices. As a result, we propose that this phenomenon could be explained by the neutralization of the solvated protons by electrons. The mechanism of this neutralization reaction probably involves tunneling of an electron from an electronegative fragment or another trap to the ͑NgHNg͒ + cation. The proposed electron-tunneling mechanism should be considered as a possible alternative to the literature models based on tunneling-assisted or radiation-induced diffusion of protons in noble-gas solids. As a novel experimental observation of this work, the efficient formation of HArF molecules occurs at 8 K in a photolyzed HF / Ar matrix. It is probable that the low-temperature formation of HArF involves local tunneling of the H atom to the Ar-F center, which in turn supports the locality of HF photolysis in solid Ar. In this model, the decay of ͑ArHAr͒ + ions and the formation of HArF molecules observed at low temperatures are generally unconnected processes; however, the decaying ͑ArHAr͒ + ions may contribute to some extent to the formation of HArF molecules.

Protons solvated in noble-gas matrices: Interaction with nitrogen

“…The radiation-accelerated tunnelling of protons can most probably be ruled out, since the decay of (NgHNg) 1 absorptions is similar under Globar radiation and in the dark. 15 The present results allow these models to be further analyzed. Based on the proton-diffusion mechanism, the decay kinetics of the relatively strongly (B1000 cm À1 ) bound (NgHNg) 1 Á Á ÁN 2 complexes and the corresponding monomers should be very different.…”

“…The annealing-induced increase of the (YHY) À (Y = Cl, Br) concentration is one of the observations supporting electron mobility leading to the YÁ Á ÁHY þ e À -(YHY) À reaction at elevated temperatures; the mobile electrons should also contribute to the neutralization of the cations. 15 Indeed, the decrease of the (NgHNg) 1 absorptions and the increase of the (YHY) À absorptions take place simultaneously upon annealing (Fig. 3).…”

“…13,14 As another possible decay mechanism, we have recently suggested a model for a neutralization reaction of (NgHNg) 1 via electron tunnelling from a local matrix environment. 15 The matrix-isolation method has been successfully used for studying intermolecular interactions for decades. 16,17 Important examples include various complexes of hydrogen halides (in particular, HCl).…”

Comparison of Hydrogen and Gold Bonding in [XHX]−, [XAuX]−, and Isoelectronic [NgHNg]+, [NgAuNg]+(X=Halogen, Ng=Noble Gas)

“…Experimental work on the series [NgHNg] + + , [XHX] À ,a nd [XAuX] À is known for some systems. [15][16][17] There are no experimental studies on the noble gas-gold cations [NgAuNg] + + known to us. Here, we report about the equilibrium structures and bond dissociation energies of the cations [NgHNg] + + and [NgAuNg] + + and the anions [XHX] À and [XAuX] À .…”

Infrared spectrum of elusive C2F radical: A matrix-isolation and computational study

“…molecule as HCCF does not have many options for products. The absorptions of solvated protons are observed after irradiation, which indicates the presence of H atoms in the matrix [21] and hence suggests the H + C 2 F dissociation channel. In addition to the identified IR-active products, positive and negative ions of C 2 H and C 2 F are possible to form.…”