Ultracold collisions in metastable helium

Photoassociation processes are studied in ultracold collisions between different isotopes of metastable He(2^3S) and He(2^3P) atoms; Penning and associative ionization rates for collisions between two He(2^3S) atoms are also obtained. Comparisons are made with data from existing experiments

Theoretical studies of photoassociation in ultracold metastable helium

Line shifts and line shapes for photoassociation of spin-polarised metastable helium to long-range vibrational states in the J = 1,0+u potential dissociating to the 2s3S1 + 2p 3P0 limit are studied using a nonperturbative multichannel calculation valid for arbitrary laser intensities. Asymptotically-free dressed states of the laser plus matter system are used to obtain the S-matrix elements required to generate the photoassociation profiles. Issues associated with the very shallow nature of the potentials that support the excited states are investigated