The B ~1PI state of NaCs:High resolution laser Induced fluorescence spectroscopy and potential construction

摘要

The lowest ~1PI state of the NaCs molecule,the 5(1) ~1PI 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)~1PI state,to obtain LAMBDA-sphttings 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 u'=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.