TY - JOUR
T1 - High densities and optical collisions in a two-colour magneto-optical trap for metastable helium
AU - Koelemeij, J.C.J.
AU - Tychkov, A.
AU - Jeltes, T.
AU - Hogervorst, W.
AU - Vassen, W.
PY - 2004
Y1 - 2004
N2 - We have studied a cloud of cold metastable helium (He*) atoms interacting with near-resonant light at 1083 nm and 389 nm. The 1083 nm light allows for efficient loading of a large magneto-optical trap (MOT) and the 389 nm light is subsequently used to increase the density and reduce the temperature of the He* cloud during a brief compression stage. Cold collisions in the cloud yield ions and fast metastables which are monitored separately using calibrated microchannel plate (MCP) detectors. We thus measure absolute production rates of ions and fast metastables escaping from the MOT during the various stages of the experiment. We observe that 389 nm optical collisions, apart from Penning ionization, produce a relatively large flux of fast metastables, which we relate to the short-range behaviour of the molecular potentials involved. Furthermore, by rapidly switching between 389 nm and 1083 nm the ratio between the respective two-body loss rate constants is determined. Using these values, together with the observed time dependence of the cloud size, the temporal behaviour of the absolute ion production rate during the compression stage is well reproduced.
AB - We have studied a cloud of cold metastable helium (He*) atoms interacting with near-resonant light at 1083 nm and 389 nm. The 1083 nm light allows for efficient loading of a large magneto-optical trap (MOT) and the 389 nm light is subsequently used to increase the density and reduce the temperature of the He* cloud during a brief compression stage. Cold collisions in the cloud yield ions and fast metastables which are monitored separately using calibrated microchannel plate (MCP) detectors. We thus measure absolute production rates of ions and fast metastables escaping from the MOT during the various stages of the experiment. We observe that 389 nm optical collisions, apart from Penning ionization, produce a relatively large flux of fast metastables, which we relate to the short-range behaviour of the molecular potentials involved. Furthermore, by rapidly switching between 389 nm and 1083 nm the ratio between the respective two-body loss rate constants is determined. Using these values, together with the observed time dependence of the cloud size, the temporal behaviour of the absolute ion production rate during the compression stage is well reproduced.
U2 - 10.1088/0953-4075/37/17/007
DO - 10.1088/0953-4075/37/17/007
M3 - Article
SN - 0953-4075
VL - 37
SP - 3501
EP - 3520
JO - Journal of Physics B: Atomic, Molecular and Optical Physics
JF - Journal of Physics B: Atomic, Molecular and Optical Physics
IS - 17
ER -