Mass scaling and nonadiabatic effects in photoassociation spectroscopy of ultracold strontium atoms

Abstract

We report photoassociation spectroscopy of ultracold 86 Sr atoms near the intercombination line and provide theoretical models to describe the obtained bound state energies. We show that using only the molecular states correlating with the 1 S 0 + 3 P 1 asymptote is insufficient to provide a mass scaled theoretical model that would reproduce the bound state energies for all isotopes investigated to date:84 Sr, 86 Sr and 88 Sr. We attribute that to the recently discovered avoided crossing between the 1 S 0potential curves at short range and we build a mass scaled interaction model that quantitatively reproduces the available 0 + u and 1 u bound state energies for the three stable bosonic isotopes. We also provide isotope-specific two-channel models that incorporate the rotational (Coriolis) mixing between the 0 + u and 1 u curves which, while not mass scaled, are capable of quantitatively describing the vibrational splittings observed in experiment. We find that the use of state-of-the-art ab initio potential curves significantly improves the quantitative description of the Coriolis mixing between the two −8 GHz bound states in 88 Sr over the previously used model potentials. We show that one of the recently reported energy levels in 84 Sr does not follow the long range bound state series and theorize on the possible causes. Finally, we give the Coriolis mixing angles and linear Zeeman coefficients for all of the photoassociation lines. The long range van der Waals coefficients C 6 (0 + u ) = 3868(50) a.u. and C 6 (1 u ) = 4085(50) a.u. are reported.

Relativistic calculations ofC6andC8coefficients for strontium dimers

“…other studies [2,13,14,17,18,[40][41][42][43]. The ab initio molecular calculations carried out using the multireference configuration interaction (MRCI) method [18] give the ground-state C 6 coefficient with excellent agreement with the recommended value of Ref.…”

“…In Table IX we summarize the results for the Sr van der Waals coefficients obtained in the present work and a Calculated via C 6 (0 u ) = C 6 (c 3 u ) and C 6 (1 u ) = (C 6 (a 3 + u ) + C 6 (c 3 u ))/2 [17,44] from Hund's case (a) values of Ref. [18].…”

“…[12][13][14]; here we provide revised value of the C 8 coefficient that has been critically evaluated for its accuracy. The energy levels of the 1 S 0 + 3 P 1 Sr 2 molecule were obtained for 88 Sr [15], 84 Sr [16], and 86 Sr [17]. In a recent paper, Borkowski et al [17] provide a theoretical model based on recent state-of-the-art ab initio potential curves from [18,19] for the description of the long-range interactions in this excited state of the strontium dimer.…”

“…The energy levels of the 1 S 0 + 3 P 1 Sr 2 molecule were obtained for 88 Sr [15], 84 Sr [16], and 86 Sr [17]. In a recent paper, Borkowski et al [17] provide a theoretical model based on recent state-of-the-art ab initio potential curves from [18,19] for the description of the long-range interactions in this excited state of the strontium dimer. They determined the van der Waals C 6 coefficients for the 0 u and 1 u bound states to be C 6 (0 u ) = 3868(50) a.u.…”

Steady-State Magneto-Optical Trap with 100-Fold Improved Phase-Space Density

“…Red MOT II(b) is the same as Red MOT II(a) except that we reduce the bandwidth of the MOT II beams to cover only −40 to −200 kHz detuning, resulting in three improvements. First, the smaller detuning of −40 kHz compresses the MOT, second, the reduced bandwidth reduces the total beam intensity required, and third, by ending the spectrum well before the photoassociation line located at −435 kHz detuning [53], we reduce losses due to molecule formation. The transfer efficiency from the top chamber to this MOT is 0.2 %, an order of magnitude lower than for Red MOT II(a).…”