Homonuclear ionizing collisions of laser-cooled metastable helium atoms

Abstract

We present a theoretical and experimental investigation of homonuclear ionizing collisions of lasercooled metastable (2 3 S1) helium atoms, considering both the fermionic 3 He and bosonic 4 He isotope. The theoretical description combines quantum threshold behavior, Wigner's spin-conservation rule and quantum statistical symmetry requirements in a single-channel model, complementing a more complete close-coupling theory that has been reported for collisions of metastable 4 He atoms. The model is supported with measurements (in the absence of light fields) of ionization rates in magnetooptically trapped samples, that contain about 3 × 10 8 atoms of a single isotope. The ionization rates are determined from measurements of trap loss due to light-assisted collisions combined with comparative measurements of the ion production rate in the absence and presence of trapping light. Theory and experiment show good agreement.

Bose-Einstein condensation and spin mixtures of optically trapped metastable helium

“…These values of K (unpol) ss are in good agreement with those measured in Refs. [31,32] and are consistent with theoretical predictions [15,23,24].…”

“…[24,32]. These experiments differ from that of the present work in that the losses resulting from interactions between individual spin states are not resolved, and instead an ionization rate K (unpol) ss is measured for the global decay of the entire unpolarized gas.…”

“…Previous measurements of the inelastic loss in unpolarized He * gases have been performed by measuring ionization rates of samples prepared in magneto-optical traps [17,[29][30][31][32], with the results of, and discrepancies among, these various measurements summarized in Refs. [24,32].…”

Trapping Cold Ground State Argon Atoms

“…All noble gas atoms have been laser cooled in a metastable state [10][11][12][13][14][15][16][17] and all but helium can be quenched to its ground state by dipole allowed transitions. However, once in their ground state they have no magnetic moment and cannot be trapped in a magnetic trap.…”

“…For most metastable atoms, the non spin-polarized loss rate is of order 10 −10 cm 3 =s [10][11][12][13][14][15][16][17] and trap lifetimes are limited by these interactions.…”