arXiv:cond-mat/0409709 · Physical Review Letters

Ultracold Li+Li2 Collisions: Bosonic and Fermionic Cases

Marko T. Cvitaš, Pavel Soldán, Jeremy M. Hutson, Pascal Honvault, Jean–Michel Launay

Published Jan 27, 2005• 104 citations

Abstract

We have carried out quantum dynamical calculations of vibrational quenching in Li + Li(2) collisions for both bosonic (7)Li and fermionic (6)Li. These are the first ever such calculations involving fermionic atoms. We find that for the low initial vibrational states considered here (v < or = 3), the quenching rates are not suppressed for fermionic atoms. This contrasts with the situation found experimentally for molecules formed via Feshbach resonances in very high vibrational states.

DOI: 10.1103/physrevlett.94.033201

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arXiv:cond-mat/0409709 · Physical Review Letters

Ultracold Li+Li2 Collisions: Bosonic and Fermionic Cases

Marko T. Cvitaš, Pavel Soldán, Jeremy M. Hutson, Pascal Honvault, Jean–Michel Launay

Published Jan 27, 2005• 104 citations

arXiv HTML PDF

Abstract

DOI: 10.1103/physrevlett.94.033201

Related papers

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We have performed a quantum-dynamical study of vibrational deexcitation and elastic scattering at ultralow collision energies for the bosonic system

^{7}\mathrm{Li}+^{7}\mathrm{Li}_{2}

and for the fermionic system

^{6}\mathrm{Li}+^{6}\mathrm{Li}_{2}

with diatomic molecules in high vibrational states. Inelastic rates show a strong and irregular dependence on the vibrational state of the diatomic molecule. For the highest vibrational state which lies near the dissociation limit, vibrational deexcitation processes are not suppressed, but rather depleted, for both bosonic and fermionic systems.

^{39}\mathrm{K}

and

^{41}\mathrm{K}

and fermions

^{40}\mathrm{K}

. At collision energies above about

0.1\phantom{\rule{0.3em}{0ex}}\mathrm{mK}

the quenching rates are well described by a classical Langevin model, but at lower energies a fully quantal treatment is essential. We find that for the low initial vibrational state considered here

(v=1)

, the ultracold quenching rates are not substantially suppressed for fermionic atoms. For both bosons and fermions, vibrational quenching is much faster than elastic scattering in the ultralow-temperature regime. This contrasts with the situation found experimentally for molecules formed via Feshbach resonances in very high vibrational states.

{\mathrm{H}}_{2}+\mathrm{He}

[Balakrishan et al. Phys. Rev. Lett. 80, 3224 (1998)] vibrational quenching. A connection is made with very recent measurements on the vibrational quenching of ultracold

{\mathrm{Cs}}_{2}

molecules in optical traps that were instead found to behave in a very different manner. Numerical experiments on the present system as well as on the

{\mathrm{H}}_{3}

reaction strongly suggest a possible explanation for such differences.

We describe the formation of fermionic NaLi Feshbach molecules from an ultracold mixture of bosonic

{}^{23}

Na and fermionic

{}^{6}

Li. Precise magnetic field sweeps across a narrow Feshbach resonance at 745 G result in a molecule conversion fraction of

5%

for our experimental densities and temperatures, corresponding to a molecule number of $5\ifmmode\times\else\texttimes\fi{}{10}^{4}$. The observed molecular decay lifetime is

1.3

ms after removing free Li and Na atoms from the trap. Due to its extremely low reactivity, NaLi molecules in the ground state will have a much longer lifetime than KRb.