P. Kowalczyk

The Li2 F 1Σg+ “shelf” state: Accurate potential energy curve based on the inverted perturbation approach

We report an accurate inverted perturbation approach (IPA) potential energy curve for the “shelf” F 1Σg+ state in Li2 which reproduces positions of the experimental energy levels available in the literature for all three isotopomers 7Li2, 6Li7Li, and 6Li2 with a standard deviation of 0.11 cm−1. Our analysis significantly improves the shape of the recently reported Rydberg–Klein–Rees (RKR) potential curve of the F 1Σg+ state [Antonova et al., J. Chem. Phys. 112, 7080 (2000)] and provides evidence for the existence of a shallow minimum in the shelf region. Using our IPA potential curve we were able to localize and identify some local perturbations in the spectra, as well as to correct the assignment of several spectral lines previously observed experimentally.

A three-section heat-pipe oven for heteronuclear alkali molecules

A heat-pipe oven is designed to produce mixed metal molecules at high concentrations. We describe the construction and operation of the novel heat pipe and illustrate its capabilities in application to the KLi molecule.

A full analytic potential energy curve for the aΣ+3 state of KLi from a limited vibrational data set

Fourier transform spectra of near-infrared laser-induced fluorescence in (39)K(6)Li show transitions to high vibrational levels of both the X (1)Sigma(+) and a (3)Sigma(+) electronic states. These include 147 transitions into six vibrational levels of the a (3)Sigma(+) state, which lie between 7 and 88 cm(-1) below the dissociation asymptote. Unfortunately, their energies span less than 30% of the well depth. However, fitting those data to eigenvalues of analytical model potential functions whose outer limbs incorporate the theoretically predicted long-range form, V(R) approximately D-C(6)R(6)-C(8)R(8), yields complete, plausible potential curves for this state. The best fits converge to remarkably similar solutions which indicate that D(e)=287(+/-4) cm(-1) and R(e)=4.99(+/-0.09) A for the a (3)Sigma(+) state of KLi, with omega(e)=47.3(+/-1.4) and 44.2(+/-1.5) cm(-1) for (39)K(6)Li and (39)K(7)Li, respectively. Properties of the resulting potential are similar to those of a published ab initio potential and are consistent with those of the analogous states of Li(2), K(2), Na(2), and NaK.

THEORETICAL STUDY OF THE ELECTRONIC STRUCTURE OF KLI AND COMPARISON WITH EXPERIMENTS

Abstract Potential energy curves have been calculated for 58 electronic states of KLi using non-empirical one-electron pseudopotentials, polarisation potentials and full-valence configuration interaction calculations. To the best of our knowledge, the present theoretical data are the first available ones for excited states of KLi. Comparisons with our previously published Rydberg–Klein–Rees curves and experimental spectroscopic constants are presented showing an overall good agreement. A long-range description for both the (1) 1, 3 Σ + states is proposed.

The c 3Σ+,b 3Π, and a 3Σ+ states of NaK revisited

We present new c 3Σ+→a 3Σ+ laser induced fluorescence spectra of the NaK molecule, which clearly indicate that v0=20 is the first vibrational level of the c 3Σ+ state lying above v=0 of B 1Π state. These spectra are used in a multistep deperturbation (B 1Π∼c 3Σ+∼b 3Π) procedure to obtain improved a 3Σ+, b 3Π and c 3Σ+ potential energy curves. The deperturbation analysis is confirmed by the calculated electronic B 1Π∼c 3Σ+ and c 3Σ+∼b 3Π spin–orbit matrix elements obtained from many-body multipartitioning perturbation theory employing the relativistic effective potential method.

On the X 1∑+ state of KLi

Laser-induced fluorescence spectra of the B–X system of 39K7Li, recorded on a Fourier transform interferometer, have allowed 47 vibrational levels of the electronic ground state to be observed. The ground state energies have been fitted to a Dunham polynomial expansion, and also directly to a numerical potential curve. Both fits reproduce the data to within the experimental accuracy of measurement (0.005 cm−1).

Time behaviour of diffuse band emission in Na2 and K2

Abstract The C states of sodium and potassium dimers were excited with short laser pulses (about 500 ps) and time evolution of the diffuse bands in Na2 (413–456 nm) and K2 (550–583 nm) was observed in fluorescence. The measured decay times were interpreted as lifetimes of unidentified triplet states giving origin to the diffuse bands. Our results contradict the values reported before.

Doppler-free spectroscopy of KLi

The B 1∏–X 1∑+ band system of the 39K7Li molecule was investigated by Doppler-free polarization spectroscopy in a heat-pipe oven. Precise molecular constants for levels v=0–3 in the ground X 1∑+ state and levels v=0–2 in the excited B 1∏ state were determined. The e-parity components in all three vibrational levels of the B state were found to be subject to rotational perturbations, assigned to interaction with the C 1∑+ state. The deperturbation analysis provided preliminary constants of the perturbing C state and values of the coupling matrix elements.

The B1Π and C1Σ+ states of KLi

Abstract The polarization labelling spectroscopy technique is used to study the B 1 Π ← X 1 Σ + and C 1 Σ + ← X 1 Σ + band systems of the KLi molecule. Accurate molecular constants are derived for the B and C states from a Dunham expansion. For the B 1 Π state our analysis covers more than 99% of the potential well depth and provides a precise value for its dissociation energy. This also allows dissociation energies of the ground X 1 Σ + state and excited C 1 Σ + state to be determined.

Line intensities in V-type polarization labelling spectroscopy of diatomic molecules

Abstract The paper presents general rules governing the intensity factors in V-type optical double-resonance polarization labelling spectroscopy. The patterns of polarization labelling spectra are investigated for each particular combination of rotational quantum numbers in 1 ∑- 1 ∑ and 1 Π - 1 ∑ electronic transitions and for circularly and linearly polarized pump laser beam. The predicted intensity distributions are compared with experimental data obtained for K 2 and Na 2 molecules at B 1 Π u ← X 1 ∑ g + probe, C 1 Π u ← X 1 ∑ g + and A 1 ∑ u + ← X 1 ∑ g + pump transitions, respectively. The obtained results show a way to optimize the polarization labelling method by making use of the whole variety of factors affecting the intensity distribution.