



01669nas a2200181   4500008004100000245010700041210006900148260001300217490000800230520098500238100002701223700002201250700002201272700002401294700001901318700001901337856013101356       2020                        eng d00aCollisions of room-temperature helium with ultracold lithium and the van der Waals bound state of HeLi0 aCollisions of roomtemperature helium with ultracold lithium and   c1/6/20200 v1013 a<p>We have computed the thermally averaged total, elastic rate coefficient for the collision of a room-temperature helium atom with an ultracold lithium atom. This rate coefficient has been computed as part of the characterization of a cold-atom vacuum sensor based on laser-cooled Li 6 or Li 7 atoms that will operate in the ultrahigh-vacuum (p&lt; 10&minus; 6 Pa) and extreme-high-vacuum (p&lt; 10&minus; 10 Pa) regimes. The analysis involves computing the X 2 Σ+ HeLi Born-Oppenheimer potential followed by the numerical solution of the relevant radial Schrödinger equation. The potential is computed using a single-reference-coupled-cluster electronic-structure method with basis sets of different completeness in order to characterize our uncertainty budget. We predict that the rate coefficient for a 300 K helium gas and a 1 μ K Li gas is 1.467 (13)&times; 10&minus; 9 cm 3/s for He 4+ Li 6 and 1.471 (13)&times; 10&minus; 9 cm 3/s for He 4+ Li 7, where the &hellip;</p>1 aMakrides, Constantinos1 aBarker, Daniel, S1 aFedchak, James, A1 aScherschligt, Julia1 aEckel, Stephen1 aTiesinga, Eite  uhttps://www.quics.umd.edu/publications/collisions-room-temperature-helium-ultracold-lithium-and-van-der-waals-bound-state-heli