Improved molecular constants for the X1Σ+ and A1Σ+ states of NaH

Improved molecular constants for the X(1)Sigma(+) and A(1)Sigma(+) states of the NaH molecule are presented, NaH molecules are produced by reactive scattering of H and Na-2 in a crossed beam experiment. High vibrational levels (6 less than or equal to upsilon " less than or equal to 9) of the NaH molecules are predominantly populated. Their excitation spectrum in the range 630 nm less than or equal to lambda less than or equal to 670 nm has been measured using a new variant of Doppler spectroscopy. The transition frequencies involving the vibrational levels 2 less than or equal to upsilon' less than or equal to 8 in the A(1)Sigma(+) and 6 less than or equal to upsilon " less than or equal to 9 in the X(1)Sigma(+) state have been determined with an accuracy of better than 0.01 cm(-1). Using also previously published data anew set of molecular constants for the X(1)Sigma(+) and A(1)Sigma(+) state is derived. In particular, the vibrational dependence of the rotational constants, D and H as well as some of upsilon "-upsilon' band origins for 0 less than or equal to upsilon " less than or equal to 9 and 0 less than or equal to upsilon' less than or equal to 25 is determined. The transition frequencies measured here or published previously are reproduced by these new coefficients with an accuracy of less than or equal to 0.1 cm(-1) [rms value] with a maximum deviation of 0.4 cm(-1). New RKR potential energy curves have been calculated up to the turning points of the levels upsilon " = 9 in the X(1)Sigma(+) state and upsilon' = 25 in the A(1)Sigma(+) state.