PHOFEX spectroscopy of HgNe and HgAr: Determination of the dissociation energies of the X¹σ⁺, A³Π ₀₊, and B³Π₁ states

Photofragment excitation (PHOFEX) spectroscopy was applied to determine the dissociation energies of the B³Π₁ states of HgAr and HgNe. The PHOFEX spectra were measured in the wavelength region where the laser-induced fluorescence spectrum of the B³Π₁-X ¹Σ⁺ transition exhibits a continuum structure by probing the photolysis product of Hg(6³P₁) through the Hg(8³S₁-6³P₁) transition. By the spectral simulation of the threshold behavior of the highresolution (Δν≈0.08 cm^-1) PHOFEX spectrum, the thresholds for the photodissociation reaction, HgRg→Hg(6³P₁)+Rg, were determined to be 39447.9(3) and 39536.0(5) cm^-1 for Rg = Ne and Ar, respectively. From these thresholds, the dissociation energies, Do's, of the B³Π₁ states of HgNe and HgAr were determined to be D_o(B³Π₁; HgNe) = 9.8(3) and D _o(B³π₁; HgAr) = 61.8(5) cm^-1, respectively. This direct determination of the dissociation energies of the B³Π₁states led to a determination of the D _o's for the X¹Σ⁺ and A ³Π₀₊ states; D₀(X¹Σ ⁺; HgNe) = 35.6(3), D₀(X¹Σ⁺; HgAr) = 123.7(5), D₀(A₃Π₀₊; HgNe) = 68.7(3), and D₀(A³Π₀₊; HgAr) = 348.8(6) cm ^-1. In addition, the (ν′,0) vibronic bands of the B ³Π¹-X¹Σ⁺ transition of HgAr were re-measured with high resolution for ν′ = 0-8. From the transition wavenumbers of these vibronic bands, the Morse potential parameters were determined with high precision as ω_e = 11.94(3) cm ^-1 and ω_cx_e = 0.594(3) cm^-1.