Polarizability of ultracold Rb2 molecules in the rovibrational ground state of a^3Σ+/u

Abstract

Abstract We study, both theoretically and experimentally, the dynamical polarizability

of

molecules in the rovibrational ground state of

. Taking all relevant excited molecular bound states into account, we compute the complex-valued polarizability

for wave numbers up to 20 000

. Our calculations are compared to experimental results at

(

) as well as at

(

). Here, we discuss the measurements at

. The ultracold Rb2 molecules are trapped in the lowest Bloch band of a 3D optical lattice. Their polarizability is determined by lattice modulation spectroscopy which measures the potential depth for a given light intensity. Moreover, we investigate the decay of molecules in the optical lattice, where lifetimes of more than

are observed. In addition, the dynamical polarizability for the

state is calculated. We provide simple analytical expressions that reproduce the numerical results for

for all vibrational levels of

as well as

. Precise knowledge of the molecular polarizability is essential for designing experiments with ultracold molecules as lifetimes and lattice depths are key parameters. Specifically the wavelength at

is of interest, since here, ultrastable high power lasers are available.