Laser Spectroscopy of the Ypjo7 States of Cr I

Here we report measured and calculated values of decay rates of the 3d(4)(D-5)4s4p(P-3(0)) y(7)P(2,3,4)(0) states of Cr I. The decay rates are measured using time-correlated single-photon counting with roughly 1% total uncertainty. In addition, the isotope shifts for transitions between these states and the ground state are measured by laser induced fluorescence to roughly 0.5% uncertainty. The decay rate calculations are carried out by a hybrid approach that combines configuration interaction and the linearized coupled-cluster method (CI+all-order method). The measurements provide a much needed precision benchmark for testing the accuracy of the CI-Pall-order approach for such complicated systems with six valence electrons, allowing us to significantly expand its applicability. These measurements also demonstrate operation of a cryogenic buffer gas beam source for future cold molecule experiments.