Stark-modulation spectroscopy of the B(1)$[^3\Pi]$ state of PbO
  We report detailed spectroscopic measurements of the X(0)$[^3\Sigma^+]$(v=0) to B(1)$[^3\Pi]$ (v=5) transition in PbO. Using a Stark-modulated laser absorption technique, we have measured the hyperfine constant of $^{207}$PbO in the B(1) state, as well as B(1)(v=5) rotational constant, X-B isotope shifts, etc. The hyperfine structure of the B(1) state is of interest as a benchmark for calculations of PbO electronic structure, related to experiments to search for the electric dipole moment of the electron. 
D. Kawall, Y. V. Gurevich, C. Cheung, S. Bickman, Y. Jiang, and D.   DeMille