Aman, J.A.Hill, J.C.Ding, R.Hazzard, Kaden R.A.Killian, T.C.Kon, W.Y.2019-01-092019-01-092018Aman, J.A., Hill, J.C., Ding, R., et al.. "Photoassociative spectroscopy of a halo molecule in 86Sr." <i>Physical Review A,</i> 98, no. 5 (2018) American Physical Society: https://doi.org/10.1103/PhysRevA.98.053441.https://hdl.handle.net/1911/105017We present two-photon photoassociation to the least-bound vibrational level of the X1Σ+g electronic ground state of the 86Sr2 dimer and measure a binding energy of Eb=−83.00(7)(20)kHz. Because of the very small binding energy, this is a halo state corresponding to the scattering resonance for two 86Sr atoms at low temperature. The measured binding energy, combined with universal theory for a very weakly bound state on a potential that asymptotes to a van der Waals form, is used to determine an s-wave scattering length a=810.6(3)(9)a0, which is consistent with, but substantially more accurate than, the previously determined a=798(12)a0 found from mass scaling and precision spectroscopy of other Sr isotopes. For the intermediate state, we use a bound level on the metastable 1S0−3P1 potential. Large sensitivity of the dimer binding energy to light near resonant with the bound-bound transition to the intermediate state suggests that 86Sr has great promise for manipulating atom interactions optically and probing naturally occurring Efimov states.engArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.Journal articlePhysRevA.98.053441https://doi.org/10.1103/PhysRevA.98.053441