An organic molecule containing krypton, HKrCCH, is reported. The preparation of HKrCCH includes 193-nm photolysis of H2C2/Kr solid mixtures at 8 K and subsequent thermal mobilization of hydrogen atoms at >/=30 K. The identification is based on infrared absorption spectroscopy and supported by ab initio calculations which show ionic and covalent contributions to the bonding. We believe that a series of similar organokrypton molecules can be prepared as computationally demonstrated for HKrC4H and HKrC3H3. These results feature a generally novel way for activating chemically the H-CC- group, which can find practical applications of the krypton catalysis.

A novel noble-gas compound, HXeOXeH, is identified using IR spectroscopy, and it seems to be the smallest known neutral molecule with two noble-gas atoms. HXeOXeH is prepared using, for example, UV photolysis of water in solid xenon and subsequent annealing at 40-45 K. The experimental observations are fully supported by extensive quantum chemical calculations. A large energy release of 8.3 eV is computationally predicted for the decomposition of HXeOXeH into the 2Xe + H2O global energy minimum. HXeOXeH may represent a first step toward the possible preparation of (Xe-O)n chains and it may be relevant to the terrestrial "missing xenon" problem.

Argon is an extremely chemically inert element. HArF is presently the only experimentally known neutral molecule containing a chemically bound argon atom. Ab initio calculations at the MP2 and CCSD͑T͒ levels presented here suggest, however, the existence of whole families of additional molecules. Explicitly predicted are FArCCH, with an argon-carbon bond, and FArSiF 3 , with an argon-silicon bond. These metastable compounds are found to be protected from decomposition by relatively high energy barriers. Other organo-argon and organo-silicon molecules derived from the above should be equally stable. The results may open the way to a substantial field of ''argon chemistry.''

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