Edward Eugene Eyler, Jonathan Mark Gilligan, Elizabeth McCormack, André Nussenzweig, & Edward Pollack, Precise two-photon spectroscopy of $E\leftarrow X^*$ intervals in H$_2$, Physical Review A 36, 3486–3489 (1987). PDF Abstract:
Edward Eugene Eyler, Jonathan Mark Gilligan, Elizabeth McCormack, André Nussenzweig, & Edward Pollack, Precise two-photon spectroscopy of $E\leftarrow X^*$ intervals in H$_2$, Physical Review A 36, 3486–3489 (1987). PDF