Photoassociation Spectroscopy of Ultracold Metastable Helium Atoms:. Numerical Analysis

We present a mapped Fourier grid method to analyse the results of a photoassociation spectroscopy experiment with metastable helium atoms in the 2³S₁ state. The ultracold atoms, close to the BEC transition, are excited with a laser that is red detuned near the 2³S₁-2³ P₀ atomic transition. Photoassociation produces giant dimers of average size up to 900 α₀ in a shallow, purely long range molecular potential 0_u^ + . The positions of five bound vibrational states in this potential are measured using a calorimetric detection. The multichannel calculations of the spectrum make use of a grid with adaptive coordinate. The precision of the measurements and of the calculations is comparable and the agreement is very good.