Accurate level energies in the EF¹, GK¹, H¹, B¹, , B′¹, , , J¹Δ_gstates of H₂

Abstract

By combining results from a Doppler-free two-photon laser excitation study on several lines in the EF 1 ' þ g À X 1 ' þ g (0,0) band of H 2 with results from a Fourier-transform spectroscopic study on a low-pressure discharge in hydrogen, absolute level energies, with respect to the X 1 AE þ g , v ¼ 0, N ¼ 0 ground level, were determined for 547 rovibronically excited states in H 2 . While for some of the levels in the EF 1 AE þ g and B 1 AE þ u states the uncertainties are as low as 0.0001 cm À1 , the accuracy of other levels is lower. The general improvement in the accuracy for the comprehensive data set of level energies is by an order of magnitude with respect to previous measurements. An updated listing of transition wavelengths of the spectral lines in the Lyman and Werner bands is presented, based on combination differences between the presently obtained B 1 AE þ u and C 1 Å u level energies and those in the X 1 AE þ g ground state.

Precision measurements and test of molecular theory in highly excited vibrational states of H2 (v = 11)

“…To extract the ground electronic X 1 Σ + g , v = 11, J level energies, from the EF-X transition energy measurements, we use the level energy values of the F(v ′ = 0) states determined by Bailly et al [50]. The derived experimental level energies are listed in Table 3, where the uncertainty is limited by the present F-X determination except for the J = 4.…”

“…Using the F level energies obtained by Bailly et al [50], the level energies of X(v = 11, J = 1, 3-5) states are derived with accuracies better than 0.002 cm −1 except for J = 3, limited by F level energy accuracy. The derived experimental values are in excellent agreement with, thereby confirming, the results obtained from the most advanced and accurate molecular theory calculations.…”

VUV Fourier-transform absorption study of the Lyman and Werner bands in D2

“…However, for weaker lines (with S/N < 6) this scatter increases to 0.05 cm −1 , and hence the total uncertainty for these lines is estimated at 0.06 cm −1 . To test the validity of the systematic error estimate of 0.01 cm −1 , the observed H 2 lines are compared with the highly accurate data by Bailly et al 33 The standard deviation of these differences is 0.05 cm −1 , and is therefore more than twice as large as the observed scattering of 0.02 cm −1 in the D 2 lines. This can be explained by the fact that the observed H 2 lines are also more than twice as broad as the unsaturated D 2 lines.…”

Perspective: Tipping the scales: Search for drifting constants from molecular spectra

“…55,56 Additional spectroscopic studies of H 2 were performed assessing the level energies in these excited states in an indirect manner, thereby verifying and even improving the transition frequencies in the Lyman and Werner bands. 57,58 The data set of laboratory wavelengths obtained for both H 2 and HD, has reached an accuracy that can be considered exact for the purpose of comparison with quasar data, where accuracies are never better than 10 −7 . A typical recording of a HD line is shown in Fig.…”