Warren T. Zemke

First observation of bound–continuum transitions in the laser‐induced A 1Σ+u–X 1Σ+g fluorescence of Na2

We report an interesting spectrum of Na2 excited by a Kr+ (5682 A) laser which shows a long series of R–P doublets in the region 5600–8000 A and a continuum with three very broad maxima beyond 8000 A. Our spectral analysis reveals that the laser populates the v′=34, J′=50 level in the A1Σ+u state from where Na2 molecules fluoresce not only to the bound vibrational levels of the entire ground state potential well (3≤v″≤56) but also to the continuum levels above the well. We have made an independent theoretical quantitative prediction of the continuous emission and the agreement between experiment and theory is found to be excellent. Almost the entire (99.6%) ground state RKR potential is constructed using the bound state experimental data which leads to a more accurate value of the dissociation energy (D″e=6024±6 cm−1). The feasibility of a continuously tunable near infrared Na2 laser based upon this radiative dissociation process is discussed. Finally, we present a comprehensive bibliography for the Na2 m...

Spectroscopy and structure of the lithium hydride diatomic molecules and ions

All significant experimental measurements and many theoretical calculations of the spectroscopy and structure of the isotopic lithium hydrides ( 6LiH, 7LiH, 6LiD, 7LiD) are identified and reviewed. Published molecular constant determinations from conventional and laser spectroscopy are evaluated; recommended spectroscopic constants for the X  1Σ+, A  1Σ+, and B  1Π states are tabulated. Potential energy curves (RKR, IPA, and hybrid) for the X  1Σ+, A  1Σ+, and B  1Π states are evaluated and recommended curves are tabulated. Dissociation energy estimates are evaluated and recommended D0 and De values tabulated for X  1Σ+, A  1Σ+, and B 1Π states. Accurate electronic structure calculations (Hartree Fock or better) on this ‘‘workbench of theoretical chemistry’’ are listed and described briefly; all excited electronic states considered are included. Experimental and theoretical radiative and dipole properties are noted and discussed. Adiabatic corrections to the Born–Oppenheimer approximation are also reviewe...

Spectroscopy and Structure of the Alkali Hydride Diatomic Molecules and their Ions

All significant experimental measurements and theoretical calculations of the spectroscopy and structure of the alkali hydrides NaH, KH, RbH, and CsH, and the corresponding alkali deuterides, are identified and reviewed. Published molecular constant determinations from conventional and laser spectroscopy are evaluated; recommended spectroscopic constants for X 1Σ+ and A 1Σ+ states are tabulated. RKR and hybrid potential energy curves are evaluated; recommended RKR curves for X 1Σ+ and A 1Σ+ states are tabulated. Ground state dissociation energy (De) estimates are evaluated; recommended X 1Σ+ and A 1Σ+ state De and D0 values are tabulated. Accurate electronic structure calculations (Hartree–Fock or better) are listed and described briefly; all excited electron states considered are included. Experimental and theoretical radiative and dipole properties are noted and discussed. Calculations on the positive and negative ions of the four diatomic alkali hydrides are also listed and described briefly.

Improved potential energy curves and dissociation energies for HF, DF and TF

Abstract We have constructed new hybrid potential energy curves for the ground states of HF, DF and TF based primarily on the experimentally based potentials of Coxon and Hajigeorgiou which include the isotopic dependence of the Born-Oppenheimer breakdown. For observed and unobserved quasibound states of HF and DF, we used these potentials and calculated quasibound energies and linewidths for various dissociation energies D e . Based on a comparison of calculated and observed line positions and widths, we determined improved D e values: for HF, D e = 49362 ± 5 cm −1 ( D 0 = 47311 cm −1 ); for DF, D e = 49346 ± 8 cm −1 ( D 0 = 47856 cm −1 ); for TF, D e = 49341 ± 9 cm −1 ( D 0 = 48093 cm −1 .

Radiative transition probalities for all vibrational levels in the X 1Σ+ state of HF

Recent analyses have led to an experimentally based potential energy curve for the ground state of HF which includes nonadiabatic corrections and which joins smoothly to the long‐range potential at an accurately determined dissociation limit (De=49 362±5 cm−1). Using this potential curve and a new ab initio dipole moment function (in excellent agreement with experiment), accurate radiative transition probabilities among all vibrational levels (v=0–19 known, v=20 predicted) of the ground state of HF have been calculated for selected rotational quantum numbers. Comparisons of Einstein A spontaneous emission coefficients, dipole moment absorption matrix elements, and Herman–Wallis factors for absorption bands are presented.

Radiative transition probabilities for the A 1Σ+–X 1Σ+ bands of 7LiH

The recently reported hybrid potential curves of Stwalley et al. [J. Chem. Phys. 66, 5412 (1977)] for the X 1Σ+ and A 1Σ+ states of LiH are combined with the ab initio transition moments of Docken and Hinze [J. Chem. Phys. 57, 4936 (1972)] to calculate radiative transition probabilities between all upper (v′?26) and all lower (v″ ?23) vibrational levels of 7LiH. By far the strongest single band found is the 23–26 band between the highest ’’long‐range’’ levels in each potential. A comparison with experimental intensity observations is made; it appears that the experiments are globally in accord with our calculations, but with some detailed differences discussed herein.

Analysis of long range dispersion and exchange interactions between two K atoms

This paper critically surveys the best available spectroscopic data for the two lowest electronic states (X ‘zc,+ and a ‘2,‘) of K2. Since both states are known up to dissociation, they can be used to determine Coulomb and exchange contributions to the intermediate and long range interaction potentials. The multipolar expansion representation of the Coulomb (dispersion) energy at long range (-Z,,C,,R-“) and the exponential representation of the exchange energy (AewaR) as well as a variety of theoretical calculations are compared with these empirical results. Finally, dissociation energy values are discussed and improved dissociation energies for the X ‘2: (D,=4449.1+ 1.0 cm-‘) and the a “2; state (0,=252.9+1.1 cm-‘) proposed.

The potential energy curves of the X 1Σ+ and A 1Σ+ states of LiH

As an important intermediate step in a long‐term project to fully understand the spectroscopy of the three lowest singlet states of LiH, (X 1Σ+, A 1Σ+, and B 1Π), we have constructed accurate hybrid potential energy curves for the X1Σ+ and A1Σ+ states to complement earlier work on the B1Π state. In each case the known Rydberg–Klein–Rees (RKR) for low vibrational levels was joined to the long‐range region of the potential (represented by new C6, C8, and C10 coefficients reported herein) fixed by the accurately known dissociation limits. The joining was obtained by scaling slightly the ab initio results of Docken and Hinze in the region of interpolation. Extrapolation to smaller distance was also done using ab initio results.

New measurements of the a3 Σ+u state of K2 and improved analysis of long‐range dispersion and exchange interactions between two K atoms

Resolved fluorescence from the K2 43 Σ+g state to the a3 Σ+u state has been measured by the perturbation‐facilitated optical–optical double resonance (PFOODR) technique. Data have been fit to an improved set of molecular constants for the a3 Σ+u state. In particular, the new Te value for this state has been determined as 4197.935±0.047 cm−1, nearly 1.8 cm−1 higher than previously reported. By combining the new results for the a3 Σ+u state and the recent results for the ground X1 Σ+g state [J. Chem. Phys. 103, 3350 (1995)], we report in this paper an improved analysis of long‐range dispersion and exchange interactions between two K atoms and of the X1 Σ+g and a3 Σ+u state dissociation energies De of 4450.674±0.072 cm−1 and 252.74±0.12 cm−1, respectively.

Radiative and nonradiative lifetimes for vibrational levels of the A 1Σ+ state of 7LiH

Newly calculated radiative transition probabilities for the A 1Σ+→X 1Σ+ (v′–v″) emission bands of 7LiH (preceding paper) are used to calculate the radiative lifetime of the various vibrational levels (0⩽v′⩽26) of A 1Σ+ LiH. For higher levels an estimate of the bound‐to‐free emission probability is also needed and included. For the highest two levels, A 1Σ+→B 1Π emission is possible and has been included, but makes a negligible contribution to the radiative lifetime. The calculated radiative lifetimes increase with v′ from 28.9 nsec at v′=0 to 36.1 nsec at v′=16 and then decrease to 27.1 nsec at v′=26. They are found to be in good agreement with measured total lifetimes, implying the nonradiative (predissociative) lifetime for the measured levels is ≳10−7 sec, in accord with simple theoretical expectations.