Observation and Characterization of the Hg‐O Diatomic Molecule: A Matrix‐Isolation and Quantum‐Chemical Investigation

Abstract

Mercuric oxide is a well-known and stable solid, but the diatomic molecule HgÀ O is very fragile and does not survive detection in the gas phase. However, laser ablation of Hg atoms from a dental amalgam alloy target into argon or neon containing about 0.3 % of 16 O 2 or of 18 O 2 during their condensation into a cryogenic matrix at 4 K allows the formation of O atoms which react on annealing to make ozone and new IR absorptions in solid argon at 521.2 cm À 1 for Hg-16 O or at 496.4 cm À 1 for Hg-18 O with the oxygen isotopic frequency ratio 521.2/496.4 = 1.0499. Solid neon gives a 529.0 cm À 1 absorption with a small 7.8 cm À 1 blue shift. CCSD(T) calculations found 594 cm À 1 for Hg 16 O and 562 cm À 1 for Hg 18 O (frequency ratio = 1.0569). Such calculations usually produce harmonic frequencies that are slightly higher than the anharmonic (observed) values, which supports their relationship. These observed frequencies have the isotopic shift predicted for HgÀ O and are within the range of recent high-level frequency calculations for the HgÀ O molecule. Spectra for the related mercury superoxide and ozonide species are also considered for the first time.