L. F. Li

Observation of the 39K2 a 3Σ+u state by perturbation facilitated optical–optical double resonance resolved fluorescence spectroscopy

Rydberg states of the potassium dimer in the 28 430–29 080 cm−1 and 30 030–30 500 cm−1 regions above the ground state X1Σ+g minimum have been studied using the perturbation facilitated optical–optical double resonance technique (PFOODR). Energy levels in these energy regions have been assigned to both triplet and singlet gerade states based on excitation pattern information as well as intensity considerations. Resolved fluorescence from a mixed triplet–singlet 43Πg ∼1Πg upper state to the ground triplet state a 3Σ+u has been used to construct a potential energy curve for the a 3Σ+u state which is in excellent agreement with recent theoretical results. Since this electronic state and the ground singlet state X1Σ+g share the same dissociation limit, we have determined the dissociation energy for the potassium dimer to be De=4450±2 cm−1.

Bound–free 1 3Π→1 3Σ+ emission from the NaK molecule: Determination of the 1 3Σ+ repulsive wall above the dissociation limit

We report the observation of bound–free emission on the 1 3Π→1 3Σ+ band of the NaK molecule. The spectra, which consist of oscillating continua in the near‐infrared, have been analyzed to determine parameters describing the repulsive wall of the 1  3Σ+ state above the dissociation limit. Spectra calculated using a potential of the form Ae−BR +C for the 1 3Σ+ state were compared to experimental spectra to yield the following values: A=5.94×105 cm−1, B=1.605 A−1, C=−220.520 cm−1. This potential, which is referenced to the bottom of the RKR 1 3Σ+ well (De =209.1 cm−1), is valid over the range R=3.4–4.5 A (R=6.4–8.5 a.u.). The relative transition dipole moment of the 1 3Π→1 3Σ+ band has also been determined over a limited range in R (7.5<R<8.9 a.u.) through the study of relative intensities of various maxima within each oscillating spectrum. In the simulated spectra, the dipole moment was represented by a functional form D(R)=m(R−R0)+D0 where D0 was used to normalize the results to a recent theoretical calcul...

Study of the 4 1Σ+g ‘‘shelf’’ state of Na2 by optical–optical double resonance spectroscopy

Due to an avoided crossing, the 4 1Σ+g state of Na2 has an unusual potential energy curve with a ‘‘shelf’’ on its outer wall. By using optical–optical double resonance techniques, vibrational levels from v=0 to 130 have been observed and the shelf was found around v=48–60. From the experimental data we have successfully constructed a Rydberg–Klein–Rees (RKR) potential curve, which can reproduce measured data with a standard deviation of 0.064 cm−1. A set of Dunham coefficients was obtained for the lower part v=0–45 of that state. Several interesting effects related to the shelf, such as the unusual behavior of Bv and Dv, of the vibrational wave functions and the semiclassical vibrational periods, and of the rotational effective potential, are discussed.

The A 1Σ+u state of the potassium dimer

Using resolved fluorescence from a 1Σ+g Rydberg state to the A 1Σ+u state of K2, we have observed the lowest vibrational levels (v’≤12) of the A 1Σ+u state. Levels v’=21 to 62 (well beyond the previously known v’=12 to 18 region) were observed using the polarization optical–optical double resonance technique. Molecular constants and a Rydberg–Klein–Rees (RKR) potential energy curve based on these constants are given. Franck–Condon factors for the K2, A 1∑+u–X 1∑+g system based on this new A 1Σ+u potential are also given.

Highly state-selective collisional energy transfer between 1Δg and 1Σ+g Rydberg states in K2

Abstract Collisional energy transfer between 1 Δ g and 1 Σ + g Rydberg states of K 2 has been studied by optical-optical double resonance (OODR) resolved fluorescence spectroscopy. The collision-induced probability for transition from a 1 Δ g state to an adjacent 1 Σ + g state of K 2 depends much more strongly on Δ J than on Δ E in each case studied. Δ J = 0 collision transfer is more favorable than Δ J = ±2, … for 1 Δ g odd J e levels. For 1 Δ g even J f levels, Δ J = ± 1 transfers are most favorable. The measurements of intensities of 1 Δ g , 1 Σ + g ← B 1 Π u , υ′ = 2, J ′ = 14e transitions and fluorescence intensities show that the collision-induced transition probability of these 1 Δ g - 1 Σ + g systems is quite large.

OODR fluorescence and polarization spectroscopy of K2: Rydberg states and the A1Σ+u state

We have observed K2 Rydberg electronic states of 1Δg and 1Σ+g symmetry using CW optical‐optical double resonance techniques in the energy range 28920–30050 cm−1 above the ground state minimum. Resolved fluorescence from the 1Σ+g states to the A1Σ+u state allows us to observe the lowest (v<12) vibrational levels of the A1Σ+u state. Using the polarization optical‐optical double resonance technique we are able to observe A1Σ+u vibrational levels in the range v=21 to 62. We are able to determine also the absolute vibrational numbering of one 1Δg Rydberg state. Major molecular constants are given for the 1Δg Rydberg state.