He Wang

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.

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.

Optical-optical double resonance spectroscopy of the Na2 21Πg state

Abstract The Na 2 2 1 Π g state has been observed from v = 0 to v = 43 (80% of the well depth) by using optical-optical double resonance spectroscopy. The Dunham coefficients and the Rydberg-Klein-Rees (RKR) potential energy curve are presented in this paper.

CW optical-optical double-resonance excitations of 39K2 Rydberg states

Abstract One 1 Δ g state, one 1 Π g state, and several 1 Σ g + states of 39 K 2 in the energy region 28 522–30 050 cm −1 have been observed by cw optical-optical double-resonance (OODR) fluorescence excitation techniques. Absolute vibrational numberings of the 1 Δ g state, the 1 Π g state, and one of the 1 Σ g + states have been assigned and major molecular constants for these three states have been determined.

Assignment of the diabatic and adiabatic atomic asymptotic limits of K2 Rydberg states

In order to make an unambiguous assignment of the atomic asymptotic limits for the previously observed Rydberg states of K2, two more low‐lying Rydberg states (one 1Δg state and one 1Πg state), were observed with sub‐Doppler resolution using cw optical–optical double resonance spectroscopy. The correlation of the molecular Rydberg states with the diabatic and adiabatic atomic limits, the quantum defects, and the diabatic and adiabatic dissociation energies are discussed and the principal quantum number assignment of Broyer et al. reinforced.

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.

The study of the 39K2 Rydberg 1Δg states by CW optical-optical double-resonance spectroscopy

Abstract Three intermediate-lying Rydberg 1Δg states of 39K2 were studied by CW optical-optical double-resonance (OODR) spectroscopy. The absolute vibrational numbering, the Dunham coefficients, the Rydberg-Klein-Rees (RKR) potential curves, and the Franck-Condon factors (FCF) of three (nd)1Δg-B1Πu systems are given. The variation with the principal quantum number n of the contribution of the ndδg Rydberg electron to the binding energy is discussed. In addition, five observed successive (nd)1Δg states included in this work (n = 8, 9, and 10) and the work of Wang et al. (J. Chem. Phys., in press) (n = 6 and 7) are assigned absolute electronic state numbering based on the molecular building-up principle. Furthermore, the dissociation limits, the dissociation energies, and the quantum defects of those (nd)1Δg states are compared with respect to the asymptotic assignments made by Broyer et al. (Chem. Phys. Lett. 99, 206–212, 1983) and by Kowalczyk et al. (Z. Phys. D. 13, 231–240, 1989); our work supports the assignment of Broyer et al.

Laser-cooled continuous Cs-beam master oscillator

In this paper, we present our design and prospects of a magneto-optical trap (MOT)-based cold Cs-beam atomic clock physics package and report the realization and characterization of a continuous, laser-cooled Cs atomic beam from a Cs MOT. We have determined the longitudinal velocity of the cold Cs beam by time of flight (TOF) method to be 7 m/s with a velocity spread of 1 m/s. By adjusting the MOT parameters, we are able to tune the Cs-beam velocity from 5 m/s to 8.5 m/s while the velocity spread remains to be 1 m/s. The Cs beam has an instantaneous atomic flux of 3.6 times 1010 atoms/s when operated in pulsed mode and a continuous beam flux of 2 times 108 atoms/s. Our theoretical simulation reveals that the MOT inhomogeneous magnetic field and the varying Doppler shift along the atomic beam propagation play an important role in determining the longitudinal velocity of the Cs atomic beam. With the cold Cs beam thus formed and a compact Ramsey cavity of 13 cm in length, we have estimated a short-term, shot-noise limited Allan standard deviation of 2.7 times 10-13 pi-frac12 (pi is the averaging time) for the atomic master oscillator under development

Metal–metal and metal–hydrogen reactive transition states

Atomic line broadening has traditionally emphasized resonance broadening by like atoms and ‘inert perturber’ broadening by rare gases and hydrogen. Such methods are ideal for qualitative and quantitative understanding of reactive transition states, including especially non-adiabatic interactions and polarization, orientation and alignment effects. Experiments at Iowa include a variety of such studies with alkali-metal and alkaline-earth metal atoms, e.g. diatomic photodissociation (including state-selected photodissociation through quasibound resonances) and reactive transition-state absorption. In each case theoretical information is available concerning the relevant potential-energy curves (or surfaces) and their couplings, and there are approximate dynamical theories (e.g. orbital locking) to be tested. A summary of recent experimental results and theoretical comparisons emphasizing diatomic photodissociation and its relation to transition state absorption will be presented.