Amanda J. Ross

Laser-induced fluorescence of NaK: the b(1) 3Π state

Laser-induced fluorescence of the NaK molecule has been recorded at high resolution by Fourier-transform spectrometry in the region 4000-9500 cm-1. Fourteen series excited by the Ar+ 4765, 4880 and 5287 AA lines have been assigned to the system D1 Pi , d3 Pi to b3 Pi . The strongest transitions, at low values of J, are Omega =1 to Omega =1, but there are also series that arise from Omega =2 to Omega =2 and from Omega =0 to Omega =0. The lower state, the second excited triplet state of NaK, has not been observed before. Constants (in cm-1) for b3 Pi 1 are as follows: Te=11562.18, omega e=120.41, omega exe=0.3425, Be=0.095066 and alpha e=3.28*10-4. The spin-orbit coupling constant A is estimated to be 15.577 cm-1 and the internuclear distance re is 3.502 AA. The results are in good agreement with pseudopotential and ab initio calculations.

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.

Spin–orbit interactions, new spectral data, and deperturbation of the coupled b 3∏u and A 1∑u+ states of K2

We report calculations of the spin–orbit energy as a function of internuclear distance R within the b 3∏u state of K2, and between the b 3∏0u and A 1∑u+ states, together with new spectroscopic data on the b state and previously unpublished data on the A state. Both the new data and previous data are fitted to Hamiltonian parameters using the discrete variable representation (DVR) method. The DVR matrix includes nonrelativistic Born–Oppenheimer potentials and spin–orbit interactions, which are scaled to match the known asymptotic limits and to best fit the experimental data. We report fitted Dunham coefficients that yield the A and b state potentials by means of the Rydberg–Klein–Rees method. These parameters thus take into account second-order spin–orbit perturbation shifts (from the vibrational levels of these two states) which are normally not considered in band-by-band fits to spectroscopic data.

Interactions between the A(1) 1Σ+u and b(1) 3Πu states of K2

Infrared laser-excited fluorescence spectra of the A(1) 1Σ+u - X(1) 1Σ+g system of K2 have been recorded at high resolution by Fourier transform spectrometry. Perturbations in A 1Σ+u are attributed to spin-orbit-induced interactions with levels of the well bound triplet state, b(1) 3Πu, and analysis leads to estimated values of molecular constants for both interacting states.

The ground state of KRb from laser-induced fluorescence

The A1 Sigma +-X1 Sigma + system of KRb was excited using a titanium-doped sapphire laser. Fluorescence spectra were recorded on a Bomem Fourier transform spectrometer, using an apodised linewidth of 0.045 cm-1. Rotational and vibrational constants are reported for the ground state, X1 Sigma +, covering the range 0<or=v<or=44 and J<141.

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).

New spectroscopic data, spin-orbit functions, and global analysis of data on the AΣu+1 and bΠu3 states of Na2

The lowest electronically excited states of Na2 are of interest as intermediaries in the excitation of higher states and in the development of methods for producing cold molecules. We have compiled previously obtained spectroscopic data on the AΣu+1 and bΠu3 states of Na2 from about 20 sources, both published and unpublished, together with new sub-Doppler linewidth measurements of about 15 000 A←X transitions using polarization spectroscopy. We also present new ab initio results for the diagonal and off-diagonal spin-orbit functions. The discrete variable representation is used in conjunction with Hund’s case a potentials plus spin-orbit effects to model data extending from v=0 to very close to the 3S2+3P1∕22 limit. Empirical estimates of the spin-orbit functions agree well with the ab initio functions for the accessible values of R. The potential function for the A state includes an exchange potential for S+P atoms, with a fitted coefficient somewhat larger than the predicted value. Observed and calculat...

An improved potential energy curve for the ground state of NaK

This paper presents an accurate potential curve for the ground state of the NaK molecule. A series of resolved laser-induced fluorescence spectra of the A-X system allowed a spread of rotational levels in the lowest 70 vibrational levels (99.9% of the total well depth) to be observed. A variational method combining the inverted perturbation approach of Vidal and Scheingraber (Vidal C R and Scheingraber H 1977 J. Mol. Spectrosc. 65 46) for short internuclear distances with an analytical expression for internuclear distances beyond 8.5 A has been used to construct a potential energy curve which reproduces the measured ground state energies with an rms error of 0.003 cm-1. The dissociation energy and coulombic parameters governing the Na(3s) + K(4s) interaction derived from this potential curve are compared with recent values.

Born–Oppenheimer breakdown in a combined-isotopomer analysis of the A 1Σu+–X 1Σg+ system of Li2

New high resolution polarization data have been obtained for the A–X band system of 6,7Li2 , and new Fourier transform data for the homonuclear lithium dimers. They are combined with earlier data for 6,6Li2 and 7,7Li2  in the first systematic combined-isotopomer analysis of data for Li2 . This analysis of 8445 rovibrational transitions yields an improved and internally consistent set of molecular constant for the three Li2 isotopomers, and determines the electronic isotope shift and leading vibrational and rotational Born–Oppenheimer breakdown correction terms for both electronic states.

The molecular constants and potential energy curve of the D1Π state in KLi

Polarisation labelling spectroscopy has been used to record the excitation spectrum of KLi in the region 18 500 to 20800cm−1. Transitions are observed to all bound levels of the D1Π state, and to some high vibrational levels of the C1Σ+ state, both of which dissociate to K(4S) + Li(2P) atoms. Spectroscopic constants are given for both electronic states. A pointwise potential curve is constructed for the D1Π state, which has a small barrier (26.5cm−1) to dissociation, located at 7.79 A.