Accurate determination of the scattering length of metastable Helium atoms using dark resonances between atoms and exotic molecules

TL;DR

This paper reports a highly precise measurement of the scattering length of metastable helium atoms using dark resonances, and demonstrates the creation of exotic molecules with microsecond lifetimes.

Contribution

It introduces a novel two-photon photoassociation spectroscopy method to determine the scattering length with unprecedented precision.

Findings

Measured the scattering length as 7.512 +/- 0.005 nm.

Achieved a measurement accuracy at least 100 times better than previous results.

Demonstrated the formation of exotic molecules with microsecond lifetimes.

Abstract

We present a new measurement of the s-wave scattering length a of spin-polarized helium atoms in the 2^3S_1 metastable state. Using two-photon photoassociation spectroscopy and dark resonances we measure the energy E_{v=14}= -91.35 +/- 0.06 MHz of the least bound state v=14 in the interaction potential of the two atoms. We deduce a value of a = 7.512 +/- 0.005 nm, which is at least one hundred 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 microsecond.