Polarizability of ultracold Rb2 molecules in the rovibrational ground state of a3Σ+u
Nadia Bouloufa-Maafa, Olivier Dulieu, Romain Véxiau, Hecker Denschlag, Johannes, Deiss, Markus, Björn Drews
Abstract
We study, both theoretically and experimentally, the dynamical polarizability α(ω) of Rb2 molecules in the rovibrational ground state of a3Σ+u. Taking all relevant excited molecular bound states into account, we compute the complex-valued polarizability α(ω) for wave numbers up to 20000cm−1. Our calculations are compared to experimental results at 1064.5nm (∼9400cm−1) as well as at 830.4nm (∼12000cm−1). Here, we discuss the measurements at 1064.5nm. 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 2s are observed. In addition, the dynamical polarizability for the X1Σ+g state is calculated. We provide simple analytical expressions that reproduce the numerical results for α(ω) for all vibrational levels of a3Σ+u as well as X1Σ+g. 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 ∼1064nm is of interest, since here, ultrastable high power lasers are available.