Rydberg spectra of ArH. Bound–bound interactions, predissociation, and radiative lifetimes of the Rydberg states

Ab initio and quantum-defect calculations for the Rydberg states of ArH

Potential energy curves were evaluated for the ground and thirteen low-lying excited electronic states of the ArH molecule over a wide range of internuclear distances by the multi-reference averaged quadratic coupled cluster method. The ab initio energy differences and transition dipole moments were used to estimate Einstein emission coefficients, absorption oscillator strengths and radiative lifetimes. Diagonal and off-diagonal quantum defects, as functions of internuclear distance, were extracted from ab initio potentials of the lowest Rydberg states of the neutral ArH molecule by taking account of configuration interaction between Rydberg series converging to the ground and two electronic excited states of the ArH(+) cation. The derived quantum-defect functions were used to generate manifolds of higher excited Rydberg states. The agreement between experimental and calculated energies and radiative transition probabilities was found to be as good as or better than that obtained by earlier calculations.

High resolution emission Fourier transform infrared spectra of the 4p-5s and 5p-6s bands of ArH

In the 2500-8500 cm(-1) region several strong emission bands of (40)ArH were observed by Fourier transform spectroscopy through a dc glow discharge in a mixture of argon and hydrogen. Rotational-electronic transitions of the two previously unstudied 4p-5s and 5p-6s,v = 0-0, bands of (40)ArH were measured and assigned in the 6060 and 3770 cm(-1) regions, respectively. A simultaneous fit of the emission transitions of the 4p-5s and 5p-6s bands and an extended set of transitions of the 6s-4p band observed by Dabrowski, Tokaryk, and Watson [J. Mol. Spectrosc. 189, 95 (1998)] and remeasured in the present work yielded consistent values of the spectroscopic parameters of the electronic states under investigation. In the branch of the 4p-5s band with transitions of type (Q)Q(f(3)e) we observed a narrowing in the linewidths with increasing rotational quantum number N. The rotational dependence of the linewidth is caused by predissociation of the 5s state by the repulsive ground 4s state through homogeneous coupling and changes in overlap integrals of the vibrational wave functions with the rotational level. Analysis was based on the Fermi's golden rule approximation model. In the 4p-5s band region a vibrational sequence ofv(')-v(")=1-1, 2-2, and 3-3 were recorded and a number of transitions belonging to the strongest (Q)Q(f(3)e) form branch of the 1-1 band were analyzed.

New Rydberg-Rydberg Transitions of the ArH and ArD Molecules

We report and rotationally analyze new spectra of the ArH and ArD molecules corresponding to the 0-0 vibrational bands of electronic transitions from the nd and ns states to the 4p Rydberg complex, in united atom notation. In ArD, our observation of the 3ddelta state, along with previous observations of the 3dpi and 3dsigma states, demonstrates that the components of the 3d state are widely separated and can be treated as Hund's case (b) states, unlike the components of the np and 4f states, which form closely coupled case (d) Rydberg complexes. The band 4dsigma --> 4p has also been assigned. The 4dpi component is known from previous work of Lipson, but as yet the 4ddelta component is unknown. Emission from the 6s and 8s states is also analyzed. From the intensities in the rotational structure, there is evidence that the 6s state interacts with the 3dsigma state. In ArH, we analyze the 0-0 bands of the 3dpi --> 4p, 3ddelta --> 4p, 4dsigma --> 4p, and 6s --> 4p transitions. Unlike the rotational levels of the 5s state, which are heavily broadened by predissociation, the 4p levels of ArH are sharp, so we can perform a more accurate and detailed analysis for this isotope than was possible previously. Qualitative features of the ArH spectra essentially mirror those of ArD, except that emission from the 3dsigma state was not identified, possibly due to a perturbation particular to this isotope. Copyright 1998 Academic Press.