Infrared spectrum of the H3N-HCl complex in solid Ne, Ne/Ar, Ar, and Kr.: Matrix effects on a strong hydrogen-bonded complex

Ammonia and hydrogen chloride vapors from thermal decomposition of NH4Cl co-deposited with excess neon at 4-5 K formed the H3N-HCl complex. Strong, broad 2084 cm(-1) and strong, sharp 1060.2, cm(-1) absorptions are assigned to the H-CI stretching and symmetric NH, bending modes and weaker 2017.4 and 708.9 cm(-1) bands to the overtone of the NH3 mode and the H-CI librational fundamental of the 1:1 complex. Complementary experiments were done with neon/argon mixtures, argon, and krypton to investigate the 1:1 complex in a range of matrix environments. Vibrational assignments are supported by (NH4Cl)-N-15. ND4Cl. and (ND4Cl)-N-15 isotopic substitution. The neon matrix spectrum suggests a strong hydrogen bond, slightly stronger than in the gas-phase complex, but not as strong as found in the argon and krypton matrix hosts owing to increased solvation by the more polarizable matrix atoms.