Direct spectroscopic determination of the Hg2 bond length and an analysis of the 2540 Å band

Abstract

The ground state bond length of the gas phase Hg2 was determined by taking high resolution spectra of an isotopically selective vibronic band of the jet-cooled molecule via the X̃(O+g)→D̃(1u) transition. The rotational structure allows a determination of the ground state equilibrium internuclear separation of Re=3.63±0.04 Å, about 0.4 Å greater than the previous accepted value from gas phase viscosity measurements. Combining this with the previously determined change in bond length between the X̃ and D̃ states (ΔRe=1.1 Å) gives a D̃-state bond length of only 2.5 Å. A careful analysis of the 2540 Å X̃(O+g)→F̃(O+u) band of the dimer, which has resisted previous analyses, shows that the band is in fact made up of a long progression of sequence bands which are virtually superimposed. Furthermore, the v″=0–v′=1 transition is about 300 times less intense than the 0–0 transition. Franck–Condon analysis leads us to conclude that the O+u potential energy curve is virtually identical to that of the ground state, with internuclear separations in the two states which differ by less than 0.02 Å.

The ab initio model potential method with the spin-free relativistic scheme by eliminating small components Hamiltonian

“…These tendencies are in agreement with the previous calculations by Yu et al 37 The best result obtained was 3.836 Å, 16.3 cm Ϫ1 , and 0.039 eV for R e , e , and D e , respectively. The discrepancies with the experimental values 38,39 are about ϩ0.2 Å, Ϫ2 cm Ϫ1 , and Ϫ0.004 eV. Our results are satisfactory at this level of theory.…”

Theory for the short-time response of small Hg n clusters after excitation

“…With this restricted potential energy surface E ( r c , R) it is possible to calculate the frequency cJc of the dimer vibration by simply integrating Newton's equation 2~c : ~/~ ~r ~Cmin drc (14) where # is the reduced mass of the oscillating system. We use rCm,~ = r~aw = 3.63A (equilibrium distance of the van der Waals bond in Hg2 [12]) as the distance at ~ = 0 and rc~,~o is determined by the condition E(rcm~,) : E(rCmo~), reflecting energy conservation. In these calculations R in E ( R , ro) is kept fixed a t /~ = R(~ = 0) = r.odW.…”

“…However, calculations for the oscillation frequencies of Hg~ [10] and Hg~ + [11] exist yielding 105cm ~ and 130cm -1, respectively. Thus the vibrational frequencies of singly and doubly charged dimer cores in a Hg,~-cluster should be rather different from that of the neutral Hg2 molecule [12]. In this paper we analyze the PES of singly and doubly ionized Hg,~ clusters by using a self-consistent electronic theory.…”

Density functional theory study of mercury adsorption on metal surfaces

“…This is very close to the Hg-Hg separation in the gas-phase Hg 2 dimer. 60 The binding energy of the Hg 2 dimer, as calculated using plane-wave DFT, is ϳ−0.033 eV at an Hg-Hg separation of 3.60 Å.…”