Resonant two-photon spectroscopy of the 2s3d D-1(2) level of neutral Be-9

We report an absolute frequency measurement of the 2s3d(1)D(2) state in neutral Be-9 using two-photon spectroscopy with a resonant intermediate state. The absolute center-of-gravity energy is determined to be 64 428.40 321(55) cm(-1), a factor of 180 more precise than the previous experimental measurement. We also confirm our previous result for the energy of the intermediate 2s2p(1)P(1) level. Precision is limited by unresolved hyperfine structure and the complications of performing resonant two-photon spectroscopy on an atomic beam. A three-level rate-equation analysis is presented to explore, and minimize, systematic uncertainties arising from small deviations of the angle between the atomic and optical beams off-perpendicular.