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 Do(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 ωe = 11.94(3) cm -1 and ωcxe = 0.594(3) cm-1.
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