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.

Forty-two vibrational (v=2–43) levels of the 7LiH C 1Σ+ excited electronic state have been observed by a pulsed optical–optical double resonance fluorescence depletion spectroscopic technique. The absolute vibrational numbering of the C 1Σ+ state is identified with the measurements of the isotopic shifts between 7LiH and 6LiH among several rotation-vibration bands of the C 1Σ+−A 1Σ+ electronic system, and it is further demonstrated by the consistency between observed spectral intensities and calculated ones. The highest observed quasi bound rotational level for the v=43 level is J=8. The spectral term values for those vibrational levels lying above v=33 occur in an irregular order. The level of v=34 lies mainly in the inner, tiny well. The term values for the observed rovibrational levels (2⩽v⩽32, 0⩽J⩽11) in the outer ionic well are described by a set of Dunham-type coefficients, with which a Rydberg–Klein–Rees (RKR) potential energy curve is constructed. This RKR potential is combined with an ab initio potential to construct an effective hybrid potential. The calculated electronic transition moment function for the C-A transition is also given.

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The nascent quantum state distributions of the RbH product resulting from the reaction of Rb(5 2 D 3/2,5/2 , 7 2 S 1/2 ) with H 2 are determined using a laser pump-probe technique. For the three investigated reactions, the nascent RbH product molecules are found to populate the lowest three vibrational (V ) 0, 1, and 2) levels of the ground electronic state. The relative vibrational populations are determined to be (0.42, 0.31, 0.27) for the Rb(5 2 D 3/2 ) + H 2 reaction, (0.42, 0.33, 0.25) for the Rb(5 2 D 5/2 ) + H 2 reaction, and (0.45, 0.32, 0.23) for the Rb(7 2 S 1/2 ) + H 2 reaction, each corresponding to a high vibrational temperature. The nascent RbH rotational temperatures are found to be slightly below the cell temperature. By comparing the spectral intensities of the RbH action spectra with those of pertinent Rb atomic fluorescence excitation spectra, the relative reactivity with H 2 for the three studied atoms is in an order of Rb(7 2 S 1/2 ) > Rb(5 2 D 3/2 ) > Rb(5 2 D 5/2 ). The relative fractions (〈f v 〉, 〈f R 〉, 〈f T 〉) of average energy disposal are derived as (0.17, 0.04, 0.79) for the Rb(5 2 D 3/2 ) case, (0.17, 0.04, 0.79) for the Rb(5 2 D 5/2 ) case, and (0.14, 0.03, 0.83) for the Rb(7 2 S 1/2 ) case, all having a major translational energy release and a minor rotational energy release. All of the above results support the assumption that the Rb*-H 2 reaction occurs primarily in a collinear C ∞V collision geometry by a harpoon mechanism, in which the crossing between the ionic Rb + H 2energy surface and the neutral Rb*-H 2 energy surfaces plays a very crucial role. A further comparison with two previous results reveals that the average vibrational disposal 〈f V 〉 in MH changes dramatically as the excited alkali atom M* is varied from K* to Rb* and to Cs*. The 〈f V 〉 value for the (K* + H 2 ) system is close to the prior distribution limit, but it becomes smaller and smaller for the (Rb* + H 2 ) system and for the (Cs* + H 2 ) system.

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 Å−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 Å (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 calculation (D0=1.07 a.u. R0=8.034 a.u.). The best fit for the parameter m was determined to be 0.121±0.029 in atomic units.