Collision-Induced Spin Depolarization of Triplet-Sigma Molecules

Abstract We performed ab initio calculations in order to assess the reactivity of ultracold RbSr ( Σ + 2 ) + RbSr ( Σ + 2 ) collisions occurring on the singlet as well as the triplet potential. At ultracold energies reactions are energetically possible if they release energy, i.e., they are exoergic. The exoergicity of reactions between RbSr molecules producing diatomic molecules are known experimentally. We extend this to reactions producing triatomic molecules by calculating the binding energy of the triatomic reaction products. We find that, in addition to the formation of Rb2 + 2Sr and Rb2 + Sr2 in singlet collisions, also the formation of Sr2Rb + Rb and Rb2Sr + Sr in both singlet and triplet collisions is exoergic. Hence, the formation of these reaction products is energetically possible in ultracold collisions. For all exoergic reactions the exoergicity is larger than 1000 cm−1. We also find barrierless qualitative reaction paths leading to the formation of singlet Rb2 + 2Sr and both singlet and triplet Rb2Sr + Sr and Sr2Rb + Rb reaction products and show that a reaction path with at most a submerged barrier exists for the creation of the singlet Rb2 + Sr2 reaction product. Because of the existence of these reactions we expect ultracold RbSr collisions to result in almost-universal loss even on the triplet potential. Our results can be contrasted with collisions between alkali-diatoms, where the formation of triatomic reaction products is endoergic, and with collisions between ultracold SrF molecules, where during triplet collisions only the spin-forbidden formation of singlet SrF2 is exoergic.Abstract We performed ab initio calculations in order to assess the reactivity of ultracold RbSr ( Σ + 2 ) + RbSr ( Σ + 2 ) collisions occurring on the singlet as well as the triplet potential. At ultracold energies reactions are energetically possible if they release energy, i.e., they are exoergic. The exoergicity of reactions between RbSr molecules producing diatomic molecules are known experimentally. We extend this to reactions producing triatomic molecules by calculating the binding energy of the triatomic reaction products. We find that, in addition to the formation of Rb2 + 2Sr and Rb2 + Sr2 in singlet collisions, also the formation of Sr2Rb + Rb and Rb2Sr + Sr in both singlet and triplet collisions is exoergic. Hence, the formation of these reaction products is energetically possible in ultracold collisions. For all exoergic reactions the exoergicity is larger than 1000 cm−1. We also find barrierless qualitative reaction paths leading to the formation of singlet Rb2 + 2Sr and both singlet and triplet Rb2Sr + Sr and Sr2Rb + Rb reaction products and show that a reaction path with at most a submerged barrier exists for the creation of the singlet Rb2 + Sr2 reaction product. Because of the existence of these reactions we expect ultracold RbSr collisions to result in almost-universal loss even on the triplet potential. Our results can be contrasted with collisions between alkali-diatoms, where the formation of triatomic reaction products is endoergic, and with collisions between ultracold SrF molecules, where during triplet collisions only the spin-forbidden formation of singlet SrF2 is exoergic.

arXiv:2108.02511New Journal of PhysicsMar 30, 20220 citations

Collisional Depolarization in the Excited State

W. E. Baylis

Springer eBooksJan 1, 197913 citations

Inelastic collisions of ultracold polar LiCs molecules with caesium atoms in an optical dipole trap

Johannes Deiglmayr, Marc Repp, Roland Wester +2 more

We investigate collisions of ultracold polar LiCs molecules and ultracold caesium atoms. LiCs molecules are formed in an optical dipole trap by photoassociation of caesium and lithium atoms via the B(1)Π excited state followed by spontaneous emission to the X(1)Σ(+) ground state and the lowest triplet state a(3)Σ(+). The molecules are then stored together with caesium atoms in the same optical trap. Rate coefficients for the loss of molecules induced by collisions with surrounding Cs atoms are measured for molecular ensembles produced via different photoassociation resonances. The results are analyzed in terms of the unitarity limit for the inelastic rates and predictions from the universal model of Idziaszek and Julienne (Phys. Rev. Lett., 2010, 104, 113202).We investigate collisions of ultracold polar LiCs molecules and ultracold caesium atoms. LiCs molecules are formed in an optical dipole trap by photoassociation of caesium and lithium atoms via the B(1)Π excited state followed by spontaneous emission to the X(1)Σ(+) ground state and the lowest triplet state a(3)Σ(+). The molecules are then stored together with caesium atoms in the same optical trap. Rate coefficients for the loss of molecules induced by collisions with surrounding Cs atoms are measured for molecular ensembles produced via different photoassociation resonances. The results are analyzed in terms of the unitarity limit for the inelastic rates and predictions from the universal model of Idziaszek and Julienne (Phys. Rev. Lett., 2010, 104, 113202).

Physical Chemistry Chemical PhysicsJan 1, 201124 citations

Mechanism for collisional transformation of atomic polarization

E. E. Nikitin

Optics and SpectroscopyMay 1, 19850 citations

Modeling of the X 1Σ+ , a 3Σ+→ E(4) 1Σ+→X 1Σ+(v=0,J=0) optical cycle for ultracold KCs molecule production

I. P. Klincare, О. Nikolayeva, M. Tamanis +3 more

We present experimental relative intensity distribution and theoretical radiative probabilities for the spin-allowed $E(4){\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}\ensuremath{-}X{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}$ and spin-forbidden $E(4){\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}\ensuremath{-}a{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}$ rovibronic transitions studied in the KCs molecule. The absorbtion and emission Einstein coefficients were predicted in a wide range of vibrational $v$ and rotational $J$ quantum numbers for both singlet-singlet $E\ensuremath{-}X$ and singlet-triplet $E\ensuremath{-}a$ rovibronic transitions along with radiative lifetimes of the upper $E$ state and branching ratios of spontaneous emission into the lower-lying electronic states, including both bound-bound and bound-continuum parts of the spectra. The required spin-allowed $E(4){\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}\ensuremath{-}X;A;C{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+};B{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}$ transition dipole moments were obtained in the framework of quasirelativistic electronic structure calculations. The regular spin-orbit coupling with the nearest ${}^{3}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}$ states is found to be sufficient to induce the spin-forbidden $E(4){\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}\ensuremath{-}a;c{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+};b{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}$ transitions by borrowing probabilities from the relevant $(1\ensuremath{-}5){\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}\ensuremath{-}(a;c){\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+};b{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}$ transitions. Relative intensity distributions in rotationally resolved $E\ensuremath{\rightarrow}X$ and $E\ensuremath{\rightarrow}a$ laser-induced fluorescence (LIF) progressions were determined from Fourier transform spectra. Experimental LIF intensity distributions demonstrated good agreement with their predicted counterparts. The simulations demonstrate that the translationally ultracold KCs molecules could be efficiently produced in their absolute ground state in one stimulated Raman step $X{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+};a{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}({v}^{\ensuremath{'}\ensuremath{'}})\ensuremath{\rightarrow}E(4){\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}({v}_{E}^{\ensuremath{'}}=44,{J}_{E}^{\ensuremath{'}}=1)\ensuremath{\rightarrow}X{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}({v}_{X}^{\ensuremath{'}\ensuremath{'}}=0,{J}_{X}^{\ensuremath{'}\ensuremath{'}}=0)$ from the weakly bound rovibronic levels ${v}^{\ensuremath{'}\ensuremath{'}}$ of both singlet $X$ and triplet $a$ states.We present experimental relative intensity distribution and theoretical radiative probabilities for the spin-allowed $E(4){\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}\ensuremath{-}X{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}$ and spin-forbidden $E(4){\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}\ensuremath{-}a{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}$ rovibronic transitions studied in the KCs molecule. The absorbtion and emission Einstein coefficients were predicted in a wide range of vibrational $v$ and rotational $J$ quantum numbers for both singlet-singlet $E\ensuremath{-}X$ and singlet-triplet $E\ensuremath{-}a$ rovibronic transitions along with radiative lifetimes of the upper $E$ state and branching ratios of spontaneous emission into the lower-lying electronic states, including both bound-bound and bound-continuum parts of the spectra. The required spin-allowed $E(4){\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}\ensuremath{-}X;A;C{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+};B{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}$ transition dipole moments were obtained in the framework of quasirelativistic electronic structure calculations. The regular spin-orbit coupling with the nearest ${}^{3}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}$ states is found to be sufficient to induce the spin-forbidden $E(4){\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}\ensuremath{-}a;c{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+};b{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}$ transitions by borrowing probabilities from the relevant $(1\ensuremath{-}5){\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}\ensuremath{-}(a;c){\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+};b{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}$ transitions. Relative intensity distributions in rotationally resolved $E\ensuremath{\rightarrow}X$ and $E\ensuremath{\rightarrow}a$ laser-induced fluorescence (LIF) progressions were determined from Fourier transform spectra. Experimental LIF intensity distributions demonstrated good agreement with their predicted counterparts. The simulations demonstrate that the translationally ultracold KCs molecules could be efficiently produced in their absolute ground state in one stimulated Raman step $X{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+};a{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}({v}^{\ensuremath{'}\ensuremath{'}})\ensuremath{\rightarrow}E(4){\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}({v}_{E}^{\ensuremath{'}}=44,{J}_{E}^{\ensuremath{'}}=1)\ensuremath{\rightarrow}X{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}({v}_{X}^{\ensuremath{'}\ensuremath{'}}=0,{J}_{X}^{\ensuremath{'}\ensuremath{'}}=0)$ from the weakly bound rovibronic levels ${v}^{\ensuremath{'}\ensuremath{'}}$ of both singlet $X$ and triplet $a$ states.

Physical Review AJun 28, 201222 citations

v

and rotational

J

quantum numbers for both singlet-singlet $E\ensuremath{-}X$ and singlet-triplet $E\ensuremath{-}a$ rovibronic transitions along with radiative lifetimes of the upper

E

state and branching ratios of spontaneous emission into the lower-lying electronic states, including both bound-bound and bound-continuum parts of the spectra. The required spin-allowed $E(4){\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}\ensuremath{-}X;A;C{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+};B{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}$ transition dipole moments were obtained in the framework of quasirelativistic electronic structure calculations. The regular spin-orbit coupling with the nearest ${}^{3}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}$ states is found to be sufficient to induce the spin-forbidden $E(4){\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}\ensuremath{-}a;c{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+};b{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}$ transitions by borrowing probabilities from the relevant $(1\ensuremath{-}5){\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}\ensuremath{-}(a;c){\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+};b{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}$ transitions. Relative intensity distributions in rotationally resolved $E\ensuremath{\rightarrow}X$ and $E\ensuremath{\rightarrow}a$ laser-induced fluorescence (LIF) progressions were determined from Fourier transform spectra. Experimental LIF intensity distributions demonstrated good agreement with their predicted counterparts. The simulations demonstrate that the translationally ultracold KCs molecules could be efficiently produced in their absolute ground state in one stimulated Raman step $X{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+};a{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}({v}^{\ensuremath{'}\ensuremath{'}})\ensuremath{\rightarrow}E(4){\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}({v}_{E}^{\ensuremath{'}}=44,{J}_{E}^{\ensuremath{'}}=1)\ensuremath{\rightarrow}X{\phantom{\rule{0.16em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}^{+}({v}_{X}^{\ensuremath{'}\ensuremath{'}}=0,{J}_{X}^{\ensuremath{'}\ensuremath{'}}=0)$ from the weakly bound rovibronic levels ${v}^{\ensuremath{'}\ensuremath{'}}$ of both singlet

X

and triplet

a

states.