L. P. Gold

Rydberg states of 7Li2 by pulsed optical–optical double resonance spectroscopy: Molecular constants of 7Li2+

Three Rydberg series of electronic states of 7Li2 have been characterized by pulsed optical–optical double resonance spectroscopy. The observed Rydberg states, which include the previously reported E 1Σ+g and G 1Πg states, have been identified as 3–10sσ 1Σ+g, 3–10dσ 1Σ+g, and 3–15dπ 1Πg. The molecular constants for several of the upper members of each of the above series have been used to deduce the ionization potential of 7Li2 and molecular constants for the X 2Σg+ state of 7Li2+. The former was determined to be T0(∞)=41 496±4 cm−1. The latter were found to be in good agreement with recent ab initio calculations.

Spectroscopic study of the E 1Σ+g ‘‘shelf’’ state in 7Li2

The E 1Σ+g ‘‘shelf ’’ state of the 7Li2 molecule was investigated using a pulsed optical optical double resonance technique. The measurements cover the vibrational levels in the range 0≤v≤29 including the shelf region around 13≤v≤15. Molecular constants have been determined. Using an inverted perturbation approach, an effective potential energy curve has been generated within the adiabatic approximation whose quantum mechanical energy eigenvalues reproduce all the measured term values to within 0.113 cm−1 for the range 0≤v≤23 and 0≤J≤47.

A spectroscopic study of the E1Σ+g and F1Σ+g states of 7Li2 by pulsed optical–optical double resonance

The results of pulsed optical–optical double resonance spectroscopic studies of the E 1S+g and F 1S+g states of 7Li2 are presented. Observations were carried out on the v = 0 through v = 30 levels of the F 1S+g state, representing about 60% of the dissociation energy. A set of Dunham molecular constants was derived and an RKR potential was generated. Franck–Condon factors were determined for the range of observed vibrational levels. The spectroscopic results on the E 1S+g state are preliminary and are included because of a probable homogeneous anticrossing between it and the F 1S+g state. It is suggested that the E 1S+g state correlates with the (2 2S)+(3 2S) atomic lithium states while the F 1S+g correlates with the (2 2P)+(2 2P) states.

A study of the E 1Σ+g state of 7Li2 by pulsed optical–optical double resonance spectroscopy

The results of pulsed optical–optical double resonance spectroscopic studies of the E 1Σ+g state of 7Li2 are presented. Observations were carried out on the v = 0 through v = 12 levels. A set of Dunham molecular constants was derived and an RKR potential was generated. Franck–Condon factors for transitions to the A 1Σ+u state were determined for the range of observed vibrational levels. An apparent deviation from the expected dissociation energy is observed consistent with the suggestion that a double minimum exists for this state.

A spectroscopic study of the G 1Πg state of 7Li2 by pulsed optical–optical double resonance

The results of a pulsed optical–optical double resonance spectroscopic study of the G 1Πg state of 7Li2 are presented. Observations were made on the v*=0 through v*=20 levels, representing about 60% of the dissociation energy. A set of Dunham molecular constants was derived. The RKR potential was generated and Franck–Condon factors were determined for the range of observed vibrational levels. A dissociation energy was estimated from a Birge–Sponer extrapolation of the Gv values which suggests a correlation with the (2 2P)+(2 2P) atomic lithium states at the dissociation limit.

The ionization potential of 7Li2 and bond energy of 7Li2

Abstract Details of an OODR study of the Rydberg states of the lithium dimer are presented which were used to arrive at a value of T O (∞) = 41496 ± 4 cm −1 for the ionization potential of 7 Li 2 . Using a more recent value for the dissociation energy of the 7 Li 2 ground electronic state, a value of D e = 10464 ± 6 cm −1 is derived for the dissociation energy of the X 2≤ g + ground state of 7 Li 2 + . These results are in serious disagreement with a recent determination in which an incorrect spectral assignment is believed to have been made.

Fine structure and Zeeman effect in the b(1)3Πu state of 6Li2 by Doppler‐free polarization spectroscopy

The fine structure of the b(1)3Πu state of the lithium dimer was observed for the first time and studied using Doppler‐free polarization spectroscopy. The triplet state was accessed by excitation of the A 1Σ+u(v=2,J=33)∼b(1)3Πu (v=9,N=32,F1,e) spin–orbit perturbed levels. The remaining two fine structure levels were excited by using the Zeeman interaction to mix levels of different J. Two polarization geometries, π pump and σ pump, were used to study separately different groups of MJ levels in magnetic fields up to 3 kG. An irreducible tensor derivation of the fine structure and Zeeman Hamiltonian matrix in Hund’s case (b) symmetrized basis functions was carried out and used to determine the perturbation parameters and the spin–spin and spin–rotation fine structure constants by a fit to the Zeeman splitting pattern. The spin–orbit contribution to the fine structure is too small in the high J states to be found accurately. The electronic spin–orbit coupling perturbation for the interaction between the sing...

Rydberg states of Li2 and molecular constants of Li+2

Abstract A Rydberg series of excited electronic states of 7 Li 2 has been characterized by pulsed optical—optical double resonance spectroscopy. Molecular constants of these states have been extrapolated to give the ionization potential of 7 Li 2 and molecular constants of the X 2 Σ + g state of 7 Li + 2 .

A pulsed optical–optical double resonance study of the 1 1Πg state of 7Li2

The results of an optical–optical double resonance study of the 1 1Πg state of 7Li2 are presented. This completes the observation and characterization of all singlet states of Li2 correlating with the Li(2s)+Li(2p) dissociation limit. Data spanning the first 31 vibrational levels were used to obtain Dunham molecular constants and a Rydberg–Klein–Rees (RKR) potential corresponding to 96% of the estimated potential well. The 1 1Πg state, which lies at Te=21 998.25  cm−1, can be characterized by a limited set of Dunham coefficients with ωe=93.354 cm−1, ωexe =−1.874 cm−1, Be=0.291 89 cm−1, and a dissociation energy De=1422.5±0.3 cm−1. The results are compared with the predictions of recent theoretical treatments.

The optical–optical double resonance spectrum of 7Li2 excited by a single tunable cw laser

The two‐photon excitation spectrum of 7Li2 produced by a single tunable cw dye laser operating between 570 and 650 nm has been observed using ultraviolet fluorescence detection. The spectrum arises from optical–optical double resonance transitions from the X 1Σg+ ground electronic state to the F 1Σg+ and G 1Πg excited states via the A 1Σu+ intermediate state, in which vibrational and rotational relaxation also take place. Using the known molecular constants for these states, a theoretically predicted spectrum was found from which the prominent lines in the experimental spectrum could be assigned. The multiphoton ionization spectrum of Li2, previously observed and interpreted in terms of bound–free–bound triplet absorption bands, can be explained as OODR transitions among the above states followed by photoionization.