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Scientific Reports

Isotopic effect on collisional widths and shifts of Hg clock transition induced by cold Rb atoms

Renu Bala, A. Linek, Marcin Witkowski, Piotr Szymon Żuchowski, M. Zawada, Paul S. Julienne, R. Ciuryło

Published Aug 4, 2026• 0 citations
Publisher

Abstract

Abstract We study the isotopic dependence of collisional widths and shifts of the Hg clock transition 1S0-3P0 perturbed by the Rbatoms in the temperature range from 1 nK to 1 K. For this purpose, we model the Born-Oppenheimer effective interactionpotential by including the leading long-range van der Waals coefficients.For elastic collisions, we show the connection betweenthe dependence of collision line shape parameters on the reduced mass of colliding partners as well as the variation of thescattering length in the excited and ground states of the Hg-Rb system in the μK temperature range. We confront the fullquantum scattering calculations with a semi-classical approximation for collisional widths and shifts. We show that the shaperesonances in excited and ground scattering states lead to significant variations of collisional line shape parameters with thechange of the reduced mass of colliding atoms. We also indicate the possible influence of inelastic collisions, which could leadto universal behavior and significantly affect the dependence of collisional broadening and shifting on the isotopic combinationof colliding atoms.

DOI
10.1038/s41598-026-63634-5

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Journal of Physics B Atomic Molecular and Optical Physics•Feb 25, 2003•45 citations
Abstract We study the isotopic dependence of collisional widths and shifts of the Hg clock transition 1S0-3P0 perturbed by the Rbatoms in the temperature range from 1 nK to 1 K. For this purpose, we model the Born-Oppenheimer effective interactionpotential by including the leading long-range van der Waals coefficients.For elastic collisions, we show the connection betweenthe dependence of collision line shape parameters on the reduced mass of colliding partners as well as the variation of thescattering length in the excited and ground states of the Hg-Rb system in the μK temperature range. We confront the fullquantum scattering calculations with a semi-classical approximation for collisional widths and shifts. We show that the shaperesonances in excited and ground scattering states lead to significant variations of collisional line shape parameters with thechange of the reduced mass of colliding atoms. We also indicate the possible influence of inelastic collisions, which could leadto universal behavior and significantly affect the dependence of collisional broadening and shifting on the isotopic combinationof colliding atoms.
We study the isotopic dependence of collisional widths and shifts of the Hg clock transition 1^11S0_00​-3^33P0_00​ perturbed by the Rb atoms in the temperature range from 1 nK to 1 K. For this purpose, we model the Born-Oppenheimer effective interaction potential by including the leading long-range van der Waals coefficients. For elastic collisions, we show the connection between the dependence of collision line shape parameters on the reduced mass of colliding partners as well as the variation of the scattering length in the excited and ground states of the Hg-Rb system in the $\upmu$K temperature range. We confront the full quantum scattering calculations with a semi-classical approximation for collisional widths and shifts. We show that the shape resonances in excited and ground scattering states lead to significant variations of collisional line shape parameters with the change of the reduced mass of colliding atoms. We also indicate the possible influence of inelastic collisions, which could lead to universal behavior and significantly affect the dependence of collisional broadening and shifting on the isotopic combination of colliding atoms.
The authors have measured the cross sections for the collisional quenching of highly excited (34<or=n<or=43) S rubidium atoms by ground-state rubidium atoms. The comparison between their data and the values calculated using a theoretical approach that only takes into account the valence electron-ground-state rubidium interaction provides the first experimental estimation of the cross section for the elastic scattering of ultra-low-energy electrons (E approximately=0.01 eV) by rubidium atoms. Their results for the quenching are connected to the available measurements of the self-broadening of the rubidium (5S-nS) lines by using a recent theoretical model: for n approximately 40 the self-broadcasting is essentially due to inelastic collisions. An upper limit is given for the cross section for the isotopic transfer between 85 Rb(nS) and 87 Rb(nS) states due to collisions with ground-state rubidium atoms.
The modified static exchange model (MSEM) recently introduced by Ray [1] to study two-atomic collision processes at low and cold-energies, is used for detailed analysis of the long-range effects due to induced dipole-dipole van der Waals interaction between Ps and H atoms. The MSEM includes the non-adiabatic short-range effect due to electron-exchange and the long-range effect due to induced dynamic dipole polarisabilities of the atoms. The effective interatomic potential is highly sensitive to the minimum distance between the atoms ( ). The s-, p- and d- wave elastic phase shifts, corresponding partial cross sections, the scattering length and effective ranges are calculated and studied with the variation of the chosen least interatomic distance between them. It is found that the scattering length is highly sensitive to the effective interatomic potential that depends on the least interatomic distance. In addition the studies are made in search of Feshbach resonances. The observed interesting feature with the variation of in the triplet channel invites more accurate investigations if new physics.
The modified static exchange model (MSEM) recently introduced by Ray [1] to study two-atomic collision processes at low and cold-energies, is used for detailed analysis of the long-range effects due to induced dipole-dipole van der Waals interaction between Ps and H atoms. The MSEM includes the non-adiabatic short-range effect due to electron-exchange and the long-range effect due to induced dynamic dipole polarisabilities of the atoms. The effective interatomic potential is highly sensitive to the minimum distance between the atoms ( ). The s-, p- and d- wave elastic phase shifts, corresponding partial cross sections, the scattering length and effective ranges are calculated and studied with the variation of the chosen least interatomic distance between them. It is found that the scattering length is highly sensitive to the effective interatomic potential that depends on the least interatomic distance. In addition the studies are made in search of Feshbach resonances. The observed interesting feature with the variation of in the triplet channel invites more accurate investigations if new physics.
We report close-coupling (CC) quantum dynamics calculations for collisional excitation/de-excitation of the lowest four rotational levels of OD − and of OH − interacting with Rb atoms in a cold ion trap. The calculations are carried out over a range of energies capable of yielding the corresponding rates for state-changing events over a rather broad interval of temperatures which cover those reached in earlier cold trap experiments. They involved sympathetic cooling of the molecular anion through a cloud of laser-cooled Rb atoms, an experiment which is currently being run again through a Heidelberg–Innsbruck collaboration. The significance of isotopic effects is analysed by comparing both systems and the range of temperatures examined in the calculations is extended up to 400 K, starting from a few mK. Both cross sections and rates are found to be markedly larger than in the case of OD − /OH − interacting the He atoms under the same conditions, and the isotopic effects are also seen to be rather significant at the energies examined in the present study. Such findings are discussed in the light of the observed trap losses of molecular anions.
For elastic scattering of 133 Cs atoms by 85 Rb and 87 Rb atoms, interacting via the X 1 Σ + and a 3 Σ + molecular states of RbCs, calculations are presented of the scattering length and the effective range and also of two volume parameters, one for low energy p-wave scattering and one for the energy of an ensemble of fermions. The calculations are performed by various methods, with several representations of the interatomic potentials, including new ab initio potentials presented here. It is shown how the calculated data may be corrected to include the influence of the long range interactions, thus removing the need for numerical solutions of the radial Schrödinger equation at very large interatomic separations. The sensitivity of the results to the choice of potentials, to the van der Waals dispersion coefficient C 6 and to the reduced mass of the colliding atoms is explored, and is found to be great.