Cold and ultracold collisions of molecular hydrogen
ORAL
Abstract
Studies of the shapes of optical resonances provide information about molecular interactions and collisions and are crucial for a proper analysis of atmospheric spectra. In molecular hydrogen, collisions significantly perturb the shape of optical resonances, leading to asymmetric line profiles and potential systematic errors in the interpretation of experimental spectra.
First, I will present our latest quantum scattering calculations performed on an ab initio potential energy surface for the H2-H2 system. We provided reference data for the analysis of the first cryogenic (T = 5 K) spectra of H2, and we demonstrated that collisional broadening and shift of a fundamental transition in H2 are dominated by one, l = 2 partial wave. This result validates the previously unexplored area of line-shape theory for physically indistinguishable molecules.
I will also discuss the results of our recent study of the effect of hyperfine and Zeeman interactions on ultracold Li – H2 collisions in the presence of an external magnetic field. We obtained a favorable ratio of the cross-sections for elastic-to-inelastic collisions for the low-field-seeking Zeeman states of H2, suggesting the feasibility of sympathetic cooling of molecular hydrogen by atomic lithium.
Finally, we explore collisions of distinguishable hydrogen isotopologues under conditions relevant to the atmospheres of giant planets. We provide ab initio collisional parameters for the strongest HD lines perturbed by H2. We demonstrate that subtle effects, such as the speed dependence of collisional broadening and shift and line narrowing, can affect the effective width and height of HD lines by a factor of 2.
First, I will present our latest quantum scattering calculations performed on an ab initio potential energy surface for the H2-H2 system. We provided reference data for the analysis of the first cryogenic (T = 5 K) spectra of H2, and we demonstrated that collisional broadening and shift of a fundamental transition in H2 are dominated by one, l = 2 partial wave. This result validates the previously unexplored area of line-shape theory for physically indistinguishable molecules.
I will also discuss the results of our recent study of the effect of hyperfine and Zeeman interactions on ultracold Li – H2 collisions in the presence of an external magnetic field. We obtained a favorable ratio of the cross-sections for elastic-to-inelastic collisions for the low-field-seeking Zeeman states of H2, suggesting the feasibility of sympathetic cooling of molecular hydrogen by atomic lithium.
Finally, we explore collisions of distinguishable hydrogen isotopologues under conditions relevant to the atmospheres of giant planets. We provide ab initio collisional parameters for the strongest HD lines perturbed by H2. We demonstrate that subtle effects, such as the speed dependence of collisional broadening and shift and line narrowing, can affect the effective width and height of HD lines by a factor of 2.
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Publication: [1] K Stankiewicz et al., in preparation<br>[2] H Jóźwiak, TV Tscherbul, P Wcisło, arxiv.org/pdf/2312.13652.pdf<br>[3] H Jóźwiak, N Stolarczyk, K Stankiewicz, M Zaborowski, D Lisak, Sz. Wójtewicz, P Jankowski, K. Patkowski, K. Szalewicz, F. Thibault, I.E. Gordon, P. Wcisło, Accurate reference spectra of HD in H2 /He bath for giant planet applications, in preparation
Presenters
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Hubert Jozwiak
Nicolaus Copernicus University in Torun
Authors
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Hubert Jozwiak
Nicolaus Copernicus University in Torun
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Piotr Wcislo
Nicolaus Copernicus University in Toruń