AIP conference proceedings

Breakup and recombination of identical bosons: He dimer-monomer collisions

J. H. Macek

Published Jan 1, 2001• 0 citations

Abstract

Three He atoms can react in vapor at temperatures of the order of a few degrees Kelvin to form a dimer and a free atom by three-body collisions. Conversely, the dimer may fragment by collisions with free He atoms. Cross sections and reaction rates for these processes have been computed at milliKelvin temperatures using the hyperspherical hidden crossing theory. At higher energies, of the order of 0.1 to 5 Kelvin, the impulse approximation has been used to estimate these processes. The computed fragmentation cross section is reported.

DOI: 10.1063/1.1395267

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AIP conference proceedings

Breakup and recombination of identical bosons: He dimer-monomer collisions

J. H. Macek

Published Jan 1, 2001• 0 citations

Publisher

Abstract

DOI: 10.1063/1.1395267

Related papers

Low-Energy Recombination of Identical Bosons by Three-Body Collisions

Esben Nielsen, J. H. Macek

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Five-body recombination of identical bosons

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The threshold recombination coefficient for three bosons whose two-body scattering length

a

is positive and large compared with the nominal range of the potentials is shown to proceed via a crossing of hyperspherical adiabatic potential curves at $R\ensuremath{\approx}2.6a$. The hidden crossing theory gives a simple expression for the rate in terms of the scattering length and a phase $\ensuremath{\Delta}$. The phase depends upon the details of the interaction, and varies from species to species, however an upper limit to the rate which depends only upon the scattering length emerges from the hidden crossing theory.

X=^{7}\text{L}\text{i}

^{23}\text{N}\text{a}

^{39}\text{K}

^{85}\text{R}\text{b}

, and

^{133}\text{C}\text{s}

, are calculated at nonzero collision energies by including not only zero total angular momentum,

J=0

, states but also

J>0

states. The three-body recombination rates show a relatively weak dependence on the alkali-metal species, differing from each other only by about one order of magnitude, except for the

^{4}\text{H}\text{e-}^{4}\text{H}\text{e-}^{23}\text{N}\text{a}

system.

We have studied hydrogen-hydrogen-alkali three-body systems in the adiabatic hyperspherical representation. For the spin-stretched case, there exists a single

X

H molecular state when

X

is one of the bosonic alkali atoms:

^{7}\mathrm{Li}

^{23}\mathrm{Na}

^{39}\mathrm{K}

^{87}\mathrm{Rb}

, or

^{133}\mathrm{Cs}

. As a result, the only recombination process is the one that leads to formation of

X

H molecules, $\text{H}+\text{H}+X\ensuremath{\rightarrow}X\text{H}+\text{H}$, and such molecules will be stable against vibrational relaxation. We have calculated the collision rates for recombination and collision-induced dissociation as well as the elastic cross sections for

\text{H}+X\text{H}

collisions up to a temperature of 0.5 K, including the partial wave contributions from ${J}^{\ensuremath{\Pi}}={0}^{+}$ to ${5}^{\ensuremath{-}}$. We have also found that there is just one three-body bound state for such systems for ${J}^{\ensuremath{\Pi}}={0}^{+}$ and no bound states for higher angular momenta.