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We present a thorough spectroscopic study of the van der Waals molecule NaNe. Our molecular beam apparatus, laser scanning system, and frequency reference technique are described in detail. Methods of rotational analysis are discussed. Descriptions of the observed vibration–rotation bands in the A 2Πr–X 2Σ+ and B 2Σ+–X 2Σ+ manifolds are presented. Perturbations in the observed spectra are discussed. Long range analysis techniques are used to determine the vibrational quantum numbering from observed isotopic shifts and to determine excited and ground state potential parameters. We find DeA=145±05 cm−1 at ReA=5.1(1)a0, DeX=8.1(9) cm−1 at ReX=10.0(1)a0, and DeB?3.0(5) cm−1 at ReB?14.4(3)a0.

We have least-squares fit 244 transitions in the mutually perturbing NaNe A 2Π–X 2Σ+ and B 2Σ+–X 2Σ+ excimer band systems using a Hund’s case ’’c’’ basis. Interatomic potentials were determined by matching computed spectroscopic parameters to 43 fitted parameters. This deperturbation analysis implies that the Na atomic angular momentum qunatum numbers—L and S—are also good molecular quantum numbers. NaNe exhibits an intramolecular transition from Hund’s case c to Hund’s case ’’a’’ angular momentum coupling as the internuclear distance is decreased. The nature of this transition is mediated by the shapes, depths, and positions of both the A 2Π and B 2Σ+ van der Waals potentials.

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Abstract.Experimental apparatus and measurement technique are described for precision absorption measurements in sodium -noble gas mixtures. The absolute absorption coefficient is measured in the wavelength range from 425 nm to 760 nm with ±2% uncertainty and spectral resolution of 0.02 nm. The precision is achieved by using a specially designed absorption cell with an accurately defined absorption path length, low noise CCD detector and double-beam absorption measurement scheme. The experimental set-up and the cell design details are given. Measurements of sodium atomic number density with ±5% uncertainty complement absorption coefficient measurements and allow derivation of the reduced absorption coefficients for certain spectral features. The sodium atomic number density is measured using the anomalous dispersion method. The accuracy of this method is improved by employing a least-squares fit to the interference image recorded with CCD detector and the details of this technique are given. The measurements are 1 aimed at stringent testing of theoretical calculations and improving the values of molecular parameters used in calculations.