arXiv:physics/0604189 · Physical Review A

Spin-dipole-induced lifetime of the least-bound Σg+5 state of He(2S13)+He(2S13)

Timothy J. Beams, G. Peach, Ian B. Whittingham

Published Jul 18, 2006• 8 citations

Abstract

The properties of the least-bound vibrational level $(v=14)$ of the $^{5}\ensuremath{\Sigma}_{g}^{+}$ state formed during the ultracold collision of two spin-polarized metastable $2\phantom{\rule{0.2em}{0ex}}^{3}S_{1}$ helium atoms are crucial to studies of photoassociation spectroscopy of metastable helium. We report a calculation of the autoionization lifetime ${\ensuremath{\tau}}_{g}$ of this state induced by spin-dipole coupling of the $^{5}\ensuremath{\Sigma}_{g}^{+}$ state to the $^{1}\ensuremath{\Sigma}_{g}^{+}$ state from which Penning and associative ionization processes are highly probable. We find ${\ensuremath{\tau}}_{g}\ensuremath{\approx}150\phantom{\rule{0.3em}{0ex}}\mathrm{\ensuremath{\mu}}\mathrm{s}$, significantly larger than the recent experimental estimates of $(0.5\ensuremath{-}3)\phantom{\rule{0.3em}{0ex}}\mathrm{\ensuremath{\mu}}\mathrm{s}$.

DOI: 10.1103/physreva.74.014702

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arXiv:physics/0604189 · Physical Review A

Spin-dipole-induced lifetime of the least-bound Σg+5 state of He(2S13)+He(2S13)

Timothy J. Beams, G. Peach, Ian B. Whittingham

Published Jul 18, 2006• 8 citations

arXiv HTML PDF

Abstract

The properties of the least-bound vibrational level

(v=14)

of the

^{5}\ensuremath{\Sigma}_{g}^{+}

state formed during the ultracold collision of two spin-polarized metastable

2\phantom{\rule{0.2em}{0ex}}^{3}S_{1}

helium atoms are crucial to studies of photoassociation spectroscopy of metastable helium. We report a calculation of the autoionization lifetime

{\ensuremath{\tau}}_{g}

of this state induced by spin-dipole coupling of the

^{5}\ensuremath{\Sigma}_{g}^{+}

state to the

^{1}\ensuremath{\Sigma}_{g}^{+}

state from which Penning and associative ionization processes are highly probable. We find

{\ensuremath{\tau}}_{g}\ensuremath{\approx}150\phantom{\rule{0.3em}{0ex}}\mathrm{\ensuremath{\mu}}\mathrm{s}

, significantly larger than the recent experimental estimates of

(0.5\ensuremath{-}3)\phantom{\rule{0.3em}{0ex}}\mathrm{\ensuremath{\mu}}\mathrm{s}

DOI: 10.1103/physreva.74.014702

Related papers

Spin-dipole-induced lifetime of the least-bound (5)Sigma(+)(g) state of He(2 S-3(1))+He(2 S-3(1))

Timothy J. Beams, G. Peach, I. B. Whittingham

The properties of the least-bound vibrational level (v=14) of the (5)Sigma(+)(g) state formed during the ultracold collision of two spin-polarized metastable 2 S-3(1) helium atoms are crucial to studies of photoassociation spectroscopy of metastable helium. We report a calculation of the autoionization lifetime tau(g) of this state induced by spin-dipole coupling of the (5)Sigma(+)(g) state to the (1)Sigma(+)(g) state from which Penning and associative ionization processes are highly probable. We find tau(g)approximate to 150 mu s, significantly larger than the recent experimental estimates of (0.5-3) mu s.The properties of the least-bound vibrational level (v=14) of the (5)Sigma(+)(g) state formed during the ultracold collision of two spin-polarized metastable 2 S-3(1) helium atoms are crucial to studies of photoassociation spectroscopy of metastable helium. We report a calculation of the autoionization lifetime tau(g) of this state induced by spin-dipole coupling of the (5)Sigma(+)(g) state to the (1)Sigma(+)(g) state from which Penning and associative ionization processes are highly probable. We find tau(g)approximate to 150 mu s, significantly larger than the recent experimental estimates of (0.5-3) mu s.

Jul 1, 20060 citations

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Physical Review ADec 1, 199945 citations

Autoionization of spin-polarized metastable helium in tight anisotropic harmonic traps

Timothy J. Beams, Ian B. Whittingham, G. Peach

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arXiv:cond-mat/0509286Physical Review LettersJan 20, 200692 citations

Decay Kinetics and Bose Condensation in a Gas of Spin-Polarized Triplet Helium

Georgy V. Shlyapnikov, Jook T. M. Walraven, U. M. Rahmanov +1 more

We consider the decay kinetics of a trapped spin-polarized gas of metastable triplet helium $^{4}\mathrm{He}(2^{3}S$ at ultralow temperatures. The sample lifetime is found to be determined by spin relaxation and Penning ionization, both induced by spin-dipole interaction in pair collisions. The rates of these processes are calculated. The Penning ionization proves to be 5 orders of magnitude slower than in the unpolarized case. The results indicate that spin-polarized triplet helium is a promising candidate for Bose-Einstein condensation.We consider the decay kinetics of a trapped spin-polarized gas of metastable triplet helium $^{4}\mathrm{He}(2^{3}S$ at ultralow temperatures. The sample lifetime is found to be determined by spin relaxation and Penning ionization, both induced by spin-dipole interaction in pair collisions. The rates of these processes are calculated. The Penning ionization proves to be 5 orders of magnitude slower than in the unpolarized case. The results indicate that spin-polarized triplet helium is a promising candidate for Bose-Einstein condensation.

Physical Review LettersDec 12, 199496 citations

The properties of the least-bound vibrational level

(v=14)

of the

^{5}\ensuremath{\Sigma}_{g}^{+}

state formed during the ultracold collision of two spin-polarized metastable

2\phantom{\rule{0.2em}{0ex}}^{3}S_{1}

helium atoms are crucial to studies of photoassociation spectroscopy of metastable helium. We report a calculation of the autoionization lifetime

{\ensuremath{\tau}}_{g}

of this state induced by spin-dipole coupling of the

^{5}\ensuremath{\Sigma}_{g}^{+}

state to the

^{1}\ensuremath{\Sigma}_{g}^{+}

state from which Penning and associative ionization processes are highly probable. We find

{\ensuremath{\tau}}_{g}\ensuremath{\approx}150\phantom{\rule{0.3em}{0ex}}\mathrm{\ensuremath{\mu}}\mathrm{s}

, significantly larger than the recent experimental estimates of

(0.5\ensuremath{-}3)\phantom{\rule{0.3em}{0ex}}\mathrm{\ensuremath{\mu}}\mathrm{s}

We describe two-photon photoassociation (PA) experiments operated in an ultracold gas of metastable

^{4}\mathrm{He}^{*}

atoms in the

2\phantom{\rule{0.2em}{0ex}}^{3}S_{1}

state. Atom-molecule dark resonances as well as Raman signals provide information on the exotic molecule in the least bound vibrational

J=2

v=14

state of the $^{5}\ensuremath{\Sigma}_{g}^{+}$ interaction potential of two spin-polarized metastable atoms. The physical origin of the various two-photon PA signals is first discussed. Their linewidths are interpreted in terms of processes limiting the lifetime $\ensuremath{\tau}$ of the exotic molecule. A value of $\ensuremath{\tau}=1.4\ifmmode\pm\else\textpm\fi{}0.3\phantom{\rule{0.3em}{0ex}}\mathrm{\ensuremath{\mu}}\mathrm{s}$ is found, which significantly differs from two recent calculations of the Penning ionization rate induced by spin-dipole coupling [T. J. Beams et al., Phys. Rev. A 74, 014702 (2006); M. Portier and G. V. Shlyapnikov (unpublished)]. The limitation of $\ensuremath{\tau}$ by atom-molecule inelastic collisions is investigated and ruled out.

A=p/q

, where

p

and

q

are integers, for those states that are degenerate in the absence of collisions or spin-dipole interactions.

We present a new measurement of the

s

-wave scattering length

a

of spin-polarized helium atoms in the

2\text{ }^{3}S_{1}

metastable state. Using two-photon photoassociation spectroscopy and dark resonances, we measure the energy ${E}_{v=14}=\ensuremath{-}91.35\ifmmode\pm\else\textpm\fi{}0.06\text{ }\text{ }\mathrm{MHz}$ of the least-bound state

v=14

in the interaction potential of the two atoms. We deduce a value of $a=7.512\ifmmode\pm\else\textpm\fi{}0.005\text{ }\text{ }\mathrm{nm}$, which is at least 100 times more precise than the best previous determinations and is in disagreement with some of them. This experiment also demonstrates the possibility to create exotic molecules binding two metastable atoms with a lifetime of the order of $1\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$.

We consider the decay kinetics of a trapped spin-polarized gas of metastable triplet helium

^{4}\mathrm{He}(2^{3}S

at ultralow temperatures. The sample lifetime is found to be determined by spin relaxation and Penning ionization, both induced by spin-dipole interaction in pair collisions. The rates of these processes are calculated. The Penning ionization proves to be 5 orders of magnitude slower than in the unpolarized case. The results indicate that spin-polarized triplet helium is a promising candidate for Bose-Einstein condensation.