Theory of vibronic interactions in D2 and H2: A comparison between multichannel-quantum-defect and coupled-equation approaches

Photodissociation of HCl in the photon energy range 14.6-15.0 eV: Channel-resolved branching ratios and fragment angular distributions

For the HCl molecule, four photodissociation channels are open in the excitation energy region 14.6-15.0 eV: H(2s) + Cl(²P_3/2), H(2p) + Cl(²P_3/2), H(2s) + Cl(²P_1/2), and H(2p) + Cl(²P_1/2). We measured the fragment angular distributions and the branching ratios of the four dissociation channels by using the extreme ultraviolet laser pump and UV laser probe, delay-time-curve, and velocity map imaging methods. The channel-resolved fragment angular distributions and fragment yield spectra show that various Rydberg states (superexcited states) contribute to the absorption cross sections, including the [A²Σ⁺]4pσ, [A²Σ⁺]4pπ, [A²Σ⁺]3dσ, [A²Σ⁺]3dπ, and [A²Σ⁺]5sσ states. Most of the H(2s) + Cl(²P_1/2) channels correlate with the ¹Σ⁺ states, while the other channels correlate with mixing excitations of the ¹Σ⁺ and ^1,3Π states. The channel branching ratios are dependent on the excitation energies. When the four channels are open, the channel branching ratios of H(2s) + Cl(²P_3/2) and H(2p) + Cl(²P_1/2) are small. Based on the recent ab initio potential energy curves, the Rydberg states converging to the ion-core A²Σ⁺ are proposed to be predissociated by the nuclear vibrational continua of the Rydberg states converging to the ion-core X²Π.

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

An extensive survey of the D(2) absorption spectrum has been performed with the high-resolution VUV Fourier-transform spectrometer employing synchrotron radiation. The frequency range of 90,000-119,000 cm(-1) covers the full depth of the potential wells of the B (1)Σ(u)(+), B' (1)Σ(u)(+), and C (1)Π(u) electronic states up to the D(1s) + D(2l) dissociation limit. Improved level energies of rovibrational levels have been determined up to respectively v = 51, v = 13, and v = 20. Highest resolution is achieved by probing absorption in a molecular gas jet with slit geometry, as well as in a liquid helium cooled static gas cell, resulting in line widths of ≈0.35 cm(-1). Extended calibration methods are employed to extract line positions of D(2) lines at absolute accuracies of 0.03 cm(-1). The D (1)Π(u) and B'' (1)Σ(u)(+) electronic states correlate with the D(1s) + D(3l]) dissociation limit, but support a few vibrational levels below the second dissociation limit, respectively, v = 0-3 and v = 0-1, and are also included in the presented study. The complete set of resulting level energies is the most comprehensive and accurate data set for D(2). The observations are compared with previous studies, both experimental and theoretical.