Unusually large polarizabilities and previously unidentified atomic states in Ba

Abstract

Electric polarizabilities of four low-J even-parity states and three low-J odd-parity states of atomic barium ranging from 35, 600 to 36, 000 cm −1 are investigated. The states of interest are excited (in an atomic beam) via an intermediate odd-parity state with a sequence of two laser pulses. The odd-parity states can be excited due to the Stark-induced mixing with even-parity states. The polarizabilities are measured via direct spectroscopy on the second-stage transition.Several states have tensor and scalar polarizabilities that exceed the values that might be expected from the known energy levels of barium by more than two orders of magnitude. Two of the Stark-induced transitions cannot be identified from the known energy spectrum of barium. The observations suggest the existence of as yet unidentified odd-parity energy states, whose energies and angular momenta are determined in the present experiment. A tentative identification of these states as [Xe]6s8p 3 P 0,2 is suggested.

High magnetic fields for fundamental physics

“…This is particularly true for the rare-earth and actinide atoms and for highly-excited states. But "new" relatively low-lying levels are being found even in lighter systems such as barium [115].…”

Stark shift and parity nonconservation for near-degenerate states of xenon

“…4, in terms of the polarizabilities and hyperpolarizabilities, following closely the work described in Ref. [16] (and references therein).…”

“…Taking the value d 1 = 1 ea 0 as the upper limit for the electric dipole transition amplitude, we note that it is about 14 times smaller than the 10s -10p 1/2 electric dipole amplitude. Assuming the same ratio for the weak matrix elements and using: In the case of barium (Ba) [16] and samarium (Sm) [17], Stark-shift measurements of various states were used to estimate the value of the reduced matrix-elements of the dipole operator to near opposite-parity "partner" states. This proved to be possible, in most cases, because the observed shifts and sublevel splittings for each state under investigation, were the result of contribution by one or a few dominating near opposite-parity partner-states in each case (which dominate due to the smallness of the energy-difference denominator).…”

“…1 (a)]. From the energy shifts and splittings of the lines, one can deduce the scalar and tensor polarizabilites, and therefore identify respective contributions from nearby opposite-parity states [16][17][18].…”

Symmetry-suppressed two-photon transitions induced by hyperfine interactions and magnetic fields

“…Note also that various properties of these and other nearby levels, including measurement of their unusually high electric polarizabilities, polarization-dependent photoionization cross-sections, and lifetimes have recently been reported in Refs. [19,20].…”