High-resolution spectra of the B1Π→X1Σ+ transition of 23Na85Rb molecule are measured by the technique of the Doppler-free optical-optical double resonance polarization spectroscopy (OODRPS). The molecular constants of the X1Σ+(v″=5-30) levels are determined, and the potential energy curve is constructed up to v″=30 by the RKR method. The time-resolved fluorescence intensity following the excitation to the B1Π(v′=5,J′= around 20) level is measured, and the lifetime of the B1Π(v′=5) level in collisionless limit is determined to be 17.8 ns. The absolute value of the electric dipole moment of the B1Π-X1Σ+ transition is determined to be 7.0 D in the region of 3.73 Å&lt
R&lt
4.98 Å. Transition lines to the (1)3Σ+ state from the B1Π(v′=8,J′ = 15) level, which is perturbed by the (1)3Π1(v0,N=J=15) level, are measured by the Doppler-free OODRPS. The energy spacing between the F1 and F3 components of the (1)3Σ+(v=4,N=15) level is observed to be smaller than 0.001 cm-1. The hyperfine splittings, which are described by Hund's case (bβS), are observed, and the hyperfine constants ANa and ARb of the (1)3Σ+(v=4) level are determined to be 0.0293 and 0.0336 cm-1, respectively. The hyperfine splittings are identified as originating from the Fermi contact interaction. From the analysis, it is concluded that the electron spins in the (1)3Σ+ state are almost equally populated to the 5SRb and 3sNa orbitals. © 1996 American Institute of Physics.