The B^1Pi <- X^1Sigma^+ system of NaCs molecule is investigated experimentally by polarization labelling spectroscopy technique. The inverted perturbation approach method is used to construct the potential energy curve of the B^1Pi state, providing a
ccurate eigenenergies for vibrational levels v = 0 - 15.
We describe a modification of the inverted perturbation approach method allowing to construct physically sensible potential energy curves for electronic states of diatomic molecules even when some parts of the potential are not adequately characteriz
ed by the experimental data. The method is based on a simple regularization procedure, imposing an additional constraint on the constructed potential curve. In the present work it is applied to the double minimum 4$^1Sigma^{+}_{mathrm u}$ state of Na$_2$, observed experimentally by polarization labeling spectroscopy technique.
We determine the inter-species s-wave triplet scattering length a3 for all K-Rb isotopic mixtures by measuring the cross-section for collisions between 41K and 87Rb in different temperature regimes. The positive value a3=+163(+57,-12)a0 ensures the s
tability of binary 41K-87Rb Bose-Einstein condensates. For the fermion-boson mixture 40K-87Rb we obtain a large and negative scattering length which implies an efficient sympathetic cooling of the fermionic species down to the degenerate regime.
We report on trapping of fermionic 40K atoms in a red-detuned standing-wave optical trap, loaded from a magneto-optical trap. Typically, 10^6 atoms are loaded at a density of 10^12 cm^-3 and a temperature of 65 microK, and trapped for more than 1 s.
The optical trap appears to be the proper environment for performing collisional measurements on the cold atomic sample. In particular we measure the elastic collisional rate by detecting the rethermalization following an intentional parametric heating of the atomic sample. We also measure the inelastic two-body collisional rates for unpolarized atoms in the ground hyperfine states, through detection of trap losses.
