The NaK 1Δ1,3 states: Theoretical and experimental studies of fine and hyperfine structure of rovibrational levels near the dissociation limit

Abstract

Earlier high-resolution spectroscopic studies of the fine and hyperfine structure of rovibrational levels of the 1 3delta state of NaK have been extended to include high lying rovibrational levels with v < or = 59, of which the highest levels lie within approximately 4 cm(-1) of the dissociation limit. A potential curve is determined using the inverted perturbation approximation method that reproduces these levels to an accuracy of approximately 0.026 cm(-1). For the largest values of v, the outer turning points occur near R approximately 12.7 angstroms, which is sufficiently large to permit the estimation of the C6 coefficient for this state. The fine and hyperfine structure of the 1 3delta rovibrational levels has been fit using the matrix diagonalization method that has been applied to other states of NaK, leading to values of the spin-orbit coupling constant A(v) and the Fermi contact constant b(F). New values determined for v < or = 33 are consistent with values determined by a simpler method and reported earlier. The measured fine and hyperfine structure for v in the range 44 < or = v < or = 49 exhibits anomalous behavior whose origin is believed to be the mixing between the 1 3delta and 1 1delta states. The matrix diagonalization method has been extended to treat this interaction, and the results provide an accurate representation of the complicated patterns that arise. The analysis leads to accurate values for A(v) and b(F) for all values of v < or = 49. For higher v (50 < or = v < or = 59), several rovibrational levels have been assigned, but the pattern of fine and hyperfine structure is difficult to interpret. Some of the observed features may arise from effects not included in the current model.

Experimental and theoretical studies of the coupledA1Σ+andbΠ<

“…Also, in this work and in [33], the electronic factor was obtained from the estimated vibronic overlap. We note also that in connection with numerous studies of more highly excited states in NaK, [34][35][36][37][38][39][40][41], various series of A state or mixed A − b state levels were observed, and term values extracted.…”

Spin–orbit coupling of the NaK 33Π and 31Π states: Determination of the coupling constant and observation of quantum interference effects

“…Heteronuclear alkali molecules have permanent dipole moments and are, therefore, of particular interest because, in principle, they can be oriented in an optical lattice [1][2][3][4][5][6][7]. In our laboratory at Lehigh University we have carried out a series of high-resolution spectroscopic studies of various excited electronic states of the heteronuclear alkali diatomic molecule NaK [8][9][10][11][12][13][14][15][16][17]. We have been particularly interested in the fine and hyperfine structure of these states and how variations in these structures with vibrational and rotational quantum numbers reflect changes in the electronic wavefunction with internuclear separation.…”

Nonadiabatic coupling in the 3Π3 and 4Π3 states of NaK

“…Several high-resolution spectroscopic studies in our laboratory have probed the fine and hyperfine structure of rovibrational levels of electronically excited triplet states of NaK. [1][2][3][4][5] As part of this program, Morgus et al 4 recently reported several anomalous features of the 3 3 ⌸ state that arise from the avoided crossing of the adiabatic potential curves corresponding to that state and the 4 3 ⌸ state. Several rovibrational level energies of the 3 3 ⌸ state could not be accurately described because they were significantly perturbed by levels of the 4 3 ⌸ state.…”

“…As in our previous experimental work, [1][2][3][4][5] we use the technique of "perturbation-facilitated, optical-optical double resonance" ͑PFOODR͒ spectroscopy to measure excitation spectra of various rovibrational levels of excited triplet states. This technique relies on two photon excitation from the singlet ground state to a highly excited triplet state through specific, mixed, intermediate "window" levels that display both singlet and triplet character.…”