The B Π 1 state of NaCs: High resolution laser induced fluorescence spectroscopy and potential construction

• Published in: The Journal of chemical physics 2007-12, Vol.127 (22), p.224302-224302-8
• Main Authors: Zaharova, J., Docenko, O., Tamanis, M., Ferber, R., Pashov, A., Knöckel, H., Tiemann, E.
• Format: Article
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.2803077

The lowest Π 1 state of the NaCs molecule, the B ( 1 ) Π 1 state, was studied using a dye laser for inducing fluorescence that was resolved by a high resolution Fourier-transform spectrometer. The presence of argon buffer gas yielded rich rotational relaxation spectra allowing to enlarge the data set for the B ( 1 ) Π 1 state, to obtain Λ -splittings and to reveal numerous local perturbations. 543 weakly perturbed energy levels for rotational quantum numbers from J ′ = 5 to 168 and vibrational quantum numbers from v ′ = 0 to 25, which cover about 87% of the potential well depth, were used for a direct pointwise fit of the potential energy curve applying the inverted perturbation approach method. The resulting potential reproduces the term values for v ′ = 0 - 7 with an experimental accuracy of about 0.01 - 0.02 cm − 1 , whereas for v ′ = 8 - 25 the deviations increase due to the perturbations, going to the order of 1 cm − 1 ; an extrapolation is made to the dissociation asymptote.