INTERACTION OF TRAPPED METASTABLE EXCITED HE ATOMS WITH SOLID NOBLE-GASES, NE, AR AND KR, INVESTIGATED BY EPR

Local metastable excited states are found in Ne, Ar and Kr cryocrystals as He gas-discharge products are trapped in the growing cryocrystals. These states are detected by EPR and are interpreted as being local metastable excited np(5)(n + 1)s(3)P(2) atomic-type states in Ne, Ar and Kr cryocrystals. Analysis of the results allows the following explanation of the observed effect to be given. For the Ne cryocrystal the effect is interpreted as a new phenomenon: quasi-resonance transfer of excitation energy from the metastable He 2(3)S(1) atom trapped in a growing neon cryocrystal to the exciton energy band of the neon crystal followed by the exciton self-trapping into the 2p(5)3p state and subsequent decay, ending in the 2p(5)3s(3)P(2) state recorded by EPR in our experiment. In the case of Ar and Kr cryocrystals the effect is explained as being due to an internal ionization of the cryocrystals by the excitation energy of trapped metastable He atoms, which implies the formation in the cryocrytal of a Rg(+) ion and a free electron in the conduction band, whereupon the fast (of 10(-12) s) self-trapping reaction of a hole follows: Rg(+) + Rg --> Rg(2)(+). Thereafter the dissociative recombination reaction Rg(2)(+) + e --> Rg(2)** --> Rg + R g*(P-3(2)) could take place.