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The insertion of Hg into H2 in a nitrogen matrix at low temperature has been induced using KrF laser irradiation, and the HgH2 produced is identified by FTIR absorption spectroscopy. This reaction is in competition with the E-V transfer from Hg(3Pi) to nitrogen, which has also been observed through the IR emission of vibrationally excited nitrogen. The spectra of isolated and complexed HgH2 have been observed. In the nitrogen matrix, annealing induces a much larger than usual frequency shift, which is related to the appearance of a vacancy close to the HgH2 at its formation. The photochemistry of the HgH2**Hg complexes at 249 nm gives a new molecule HHgHgH, which may be dissociated. The isolated HgH2 is shown to be very stable under 249 nm irradiation and is found to dissociate under 193 nm irradiation. All the absorption studies have also been done with deuterated compounds, and the force constants of the HgH bonds of the new molecules have been determined.

By highly resolved infrared absorption spectra the dependence of aggregation of NO in neon on concentration, annealing, and deposition temperature is studied in recording the intensities of monomers in two sites (1874.54 and 1877.56 cm−1), of cis-(NO)2 dimers in the symmetrical (around 1866 cm−1) and antisymmetrical (around 1780 cm−1) mode, of a special dimer around 1858 cm−1 and a series of monomer side bands shifted by about 0.3, 0.6, and 1.8 cm−1 due to coupling of molecules at different lattice sites. The dimer bands also exhibit a fine structure and a broad background caused by larger aggregates. The almost statistical size distribution at low concentration and condensation temperature changes to a preferential aggregation at higher concentration (≳2×10−3) and condensation temperature (≥7 K) and the irreversible aggregation by diffusion at elevated temperatures is followed on a time scale of hours. A reversible conversion of special dimers at 1778.67 and 1865.48 cm−1 to a dimer at 1857.93 cm−1 is accelerated by lowering the temperature and attributed to a martensitic hcp to fcc phase transition.

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