Measurement of absolute transition dipole moment functions

We describe a two-laser experiment using optical-optical double resonance fluorescence and Autler– Townes AT splittings to determine the NaK 3 1 →1 X 1 +, 2 A 1 + absolute transition dipole moment functions. Resolved 3 1 →A 1 + and 3 1 →X 1 + fluorescence was recorded with the frequencies of a titanium-sapphire laser L1 and a ring dye laser L2 fixed to excite particular 3 1 =19,J=11, f ←A 1 + ,J =J=11,e ←X 1 + ,J =J 1,e double resonance transitions. The coefficients of a trial transition dipole moment function e R =a0+a1 Req /R 2 +a2 Req /R 4+ . . . were adjusted to match the relative intensities of resolved spectral lines terminating on the lower A 1 + ,11,e and X 1 + ,11,e levels. These data provide a relative measure of the functions e R over a broad range of R. Next, L2 was tuned to either the 3 1 19,11, f ←A 1 + 10,11,e or 3 1 19,11, f ←A 1 + 9,11,e transition and focused to an intensity large enough to split the levels via the AT effect. L1 was scanned over the A 1 + 10,11,e ←X 1 + 1,10,e or A 1 + 9,11,e ←X 1 + 0,12,e transition to probe the AT line shape, which was fit using density matrix equations to yield an absolute value for ik = vib i R e R vib k R dR, where i and k represent the upper and lower levels, respectively, of the coupling laser L2 transition. Finally, the values of ik were used to place the relative e R functions obtained with resolved fluorescence onto an absolute scale. We compare our experimental transition dipole moment functions to the theoretical work of Magnier et al. J. Mol. Spectrosc. 200, 96 2000 . © 2008 American Institute of Physics. DOI: 10.1063/1.2982780