Gerade/ungerade symmetry- breaking in HD at the n =2 dissociation limit
We report on a study of the I'1Πg outer well state of HD. Via a resonance-enhanced XUV + IR (extreme ultraviolet + infrared) excitation scheme, rovibronic levels (v = 0-2, J = 1-4) are populated and probed by pulsed lasers. Level energies are measured with an accuracy of 0.03 cm-1. Due to gerade-ungerade symmetry breaking, the long-range behavior of the I' potential in HD deviates from that of H2 and D2. When this deviation is taken into account a semi-empirical potential for the I'1Πg state may be constructed, resulting in better agreement with the observed level energies than derived from an adiabatic ab initio potential. With this new potential it is predicted that the I' well can sustain only 4 vibrational levels, with the v = 3 level having a binding energy of 1.38(3) cm-1. PACS Nos.: 33.80.Rv, 34.20.Cf, 33.20.Ni, 31.50.+w
Some Excited States of the Hydrogen Molecule. II. 1Πg(1s2pπ), 3Πg(1s2pπ), 1Δg(1s3dδ), 3Δg(1s3dδ), 1Δu(1s3dδ), 3Δu(1s3dδ)
Complete theoretical potential curves for the bound 1Δg(1s3dδ) and 3Δg(1s3dδ) states of H2 and for the long‐range portions of the repulsive 1πg(1s2pπ), 3πg(1s2pπ), 1Δu(1s3dδ), and 3Δu(1s3dδ) states of H2 are reported. Comparison of these results plus results from Paper I of this series to the conventional perturbation theory computations for the long‐range interactions of those states shows that the conventional perturbation results may be misleading if ``valence'' and ``overlap'' forces are not considered. The computed total energies at Re for the 1Δg(1s3dδ) and 3Δg(1s3dδ) states are —0.6570143 (—0.65778), and —0.6571785 (—0.65872 a.u.), respectively. The values in parentheses are experimental values. Spectroscopic constants and expectation values for some one‐electron operators for the 1Δg(1s3dδ) and 3Δg(1s3dδ) states are also presented. Two‐center and one‐center wavefunctions yielding comparable energies for the 1Δg(1s3dδ) state are compared through expectation values for a series of one‐electron opera...
Multiphoton excitation of high singlet np Rydberg states of molecular hydrogen: Spectroscopy and dynamics.
We have used two-step, two-color excitation to populate high np singlet Rydberg states of molecular hydrogen under electric-field-free conditions. Sub-Doppler resolution is obtained by exciting the X /sup 1/..sigma../sub g//sup +/..-->..E /sup 1/..sigma../sub g//sup +/ two-photon transition with copropagating photons, then further exciting the molecules to high Rydberg states with a narrow-band laser. We have observed transitions to states up to n--90 for the Rydberg series which converge to the two lowest ionization limits. From an analysis of the energies of the observed transitions we have obtained new results for the first two ionization potentials of molecular hydrogen, with the highest accuracy reported to date. The new values are 124 417.61 +- 0.07 cm/sup -1/ for parahydrogen and 124 475.94 +- 0.07 cm/sup -1/ for orthohydrogen. Some of the Rydberg states predissociate strongly, apparently due to the influence of perturbing states of low principle quantum number. This is the first observation of such predissociation in Rydberg states of high principle quantum number.