Ab Initio Calculations of the Static and Dynamic Polarizability of BaOH

TL;DR

This work delivers high-precision ab initio predictions of the static and dynamic polarizabilities of $^{138}$BaOH using relativistic coupled-cluster theory, with rigorous uncertainty quantification that accounts for basis-set, relativistic, correlation, and vibrational effects. Static properties were obtained via a finite-field approach with X2C/CCSD(T) treatment, while dynamic properties at 1064 nm were computed with NR LR theory using an ECP for relativistic effects and then anchored to the accurate static limit to constrain uncertainties. The results yield $oldsymbol{ m eta_ ext{||}}(0)=200.3(24)$ a.u., $oldsymbol{ m eta_ ext{⊥}}(0)=298(5)$ a.u., and a dipole moment of $oldsymbol{oldsymbol{ m oldsymbol{oldsymbol{oldsymbol{ m oldsymbol{ u}}}}}}=0.583(11)$ a.u., with dynamic values at 1064 nm of $oldsymbol{eta_ ext{||}}(1064 ext{ nm}) o 357(31)$ a.u. and $oldsymbol{eta_ ext{⊥}}(1064 ext{ nm}) o 714(29)$ a.u. The vibrational corrections are small but included, and cross-method validation against DC-LRCCSD confirms the robustness of the approach. These polarizabilities enable precise trap-depth estimates and scattering-rate assessments for BaOH in optical traps, informing the design of next-generation eEDM experiments employing BaOH in the (010) bending state.

Abstract

We present high-precision ab initio calculations of the static and dynamic polarizability of the barium monohydroxide ($^{138}$BaOH) molecule, using relativistic coupled-cluster theory. By thoroughly investigating the dependence of the calculated polarizabilities on computational parameters (basis set size, treatment of relativity, level of treatment of electron correlation, and vibrational corrections), a procedure to determine uncertainties is constructed and applied. The dipole moment of BaOH is also calculated and compared to experiment, confirming the accuracy of the predicted polarizabilities. The static and dynamic ($λ=1064\;\text{nm}$) polarizability was calculated for both the ground state and the (010) vibrational bending mode, the latter state being particularly interesting for a wide range of quantum experiments. The ground state static polarizabilities were calculated to be 200.8(24) a.u. and 297(5) a.u. for the parallel and perpendicular components respectively.

Figures (1)

• Figure 1: Parallel and perpendicular components of the dynamic polarizability (solid lines) with uncertainty bounds (shaded regions) as a function of the frequency of the external electric field. The dashed line corresponds to the 1064 nm laser.