Infrared Emission Spectra and Equilibrium Structures of Gaseous HgH₂ and HgD₂

Abstract

A detailed analysis of the high-resolution infrared emission spectra of gaseous HgH2 and HgD2 in the 1200-2200 cm(-1) spectral range is presented. The nu3 antisymmetric stretching fundamental bands of 204HgH2, 202HgH2, 201HgH2, 200HgH2, 199HgH2, 198HgH2, 204HgD2, 202HgD2, 201HgD2, 200HgD2, 199HgD2, and 198HgD2, as well as a few hot bands involving nu1, nu2, and nu3 were analyzed rotationally, and spectroscopic constants were obtained. Using the rotational constants of the 000, 100, 01(1)0, and 001 vibrational levels, we determined the equilibrium rotational constants (B(e)) of the most abundant isotopologues, 202HgH2 and 202HgD2, to be 3.135325(24) cm(-1) and 1.569037(16) cm(-1), respectively, and the associated equilibrium Hg-H and Hg-D internuclear distances (re) are 1.63324(1) A and 1.63315(1) A, respectively. The re distances of 202HgH2 and 202HgD2 differ by about 0.005%, which can be attributed to the breakdown of the Born-Oppenheimer approximation.

Calculated spectroscopic properties of HgH2

“…Threedimensional spline interpolation was used to represent the PP/MRCI+Q potential energy surface, from which rotationless (J = 0) vibrational term energies and wavefunctions were computed by means of a direct product discrete variable representation (DVR). In comparison with the precise experimental results now available [4], the wavenumbers of the antisymmetric stretching vibrations (ν 3 ) of 202 HgH 2 and 202 HgD 2 were underestimated by 27.2 and 20.5 cm -1 , respectively.…”

“…The SO-CI describes the second-order SO effects for HgH 2 , together with electron correlation effects, by including all single and double excitations from the closed-shell singlet ground state with spin symmetries up to quintet. The SO energy contribution determined this way at the experimental equilibrium geometry [4] is -0.1386 E h , i.e., less than 0.1% of the scalar-relativistic CISD energy.…”

“…For states with l ≠ 0, the following formula was employed: In equation [4], E e and E f denote the rovibrational term energy of the vibrational level under consideration in the so called e-block and f-block, respectively. The l-type doubling constants q v and q J were obtained through least-squares fit with an expression on the form:…”

“…Although the existence of solid mercury dihydride (HgH 2 ) has been known for more than half a century [1,2], it was only recently that molecular HgH 2 could be investigated by means of highresolution spectroscopy [3,4]. Gaseous HgH 2 and its deuterated isotopomers were synthesized through the reaction of mercury vapour with molecular hydrogen or deuterium in the presence of a dc electrical discharge.…”

A theoretical study of ZnH2: a case of very strong Darling–Dennison resonance

“…In a series of papers by Bernath and coworkers, three dihydrides of group 12 transition metals (ZnH 2 , CdH 2 and HgH 2 ) have been studied by high-resolution infrared emission spectroscopy and a wealth of precise information on various rovibrational transitions of different isotopomers could be obtained [1][2][3][4][5][6]. The largest amount of spectroscopic data was collected for ZnH 2 isotopomers.…”