Nonadiabatic laser-induced alignment dynamics of alkali dimers on the surface of a helium droplet
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| Format: | Preprint |
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2025
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| _version_ | 1866916622831190016 |
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| author | Kristensen, Henrik H. Kranabetter, Lorenz Ghazaryan, Areg Schouder, Constant A. Hansen, Emil Jensen, Frank Zillich, Robert E. Lemeshko, Mikhail Stapelfeldt, Henrik |
| author_facet | Kristensen, Henrik H. Kranabetter, Lorenz Ghazaryan, Areg Schouder, Constant A. Hansen, Emil Jensen, Frank Zillich, Robert E. Lemeshko, Mikhail Stapelfeldt, Henrik |
| contents | Alkali dimers, $\mathrm{Ak}_2$, located on the surface of a helium nanodroplet, are set into rotation through the polarizability interaction with a nonresonant 1-ps-long laser pulse. The time-dependent degree of alignment is recorded using femtosecond-probe-pulse-induced Coulomb explosion into a pair of $\mathrm{Ak}^+$ fragment ions. The results, obtained for $\mathrm{Na}_2$, $\mathrm{K}_2$, and $\mathrm{Rb}_2$ in both the ground state $1 ^1Σ_g^+$ and the lowest-lying triplet state $1 ^3Σ_u^+$, exhibit distinct, periodic revivals with a gradually decreasing amplitude. The dynamics differ from that expected for dimers had they behaved as free rotors. Numerically, we solve the time-dependent rotational Schrödinger equation, including an effective mean-field potential to describe the interaction between the dimer and the droplet. The experimental and simulated alignment dynamics agree well and their comparison enables us to determine the effective rotational constants of the alkali dimers with the exception of $\mathrm{Rb}_2$($1 ^3Σ_u^+$) that only exhibits a prompt alignment peak but no subsequent revivals. For $\mathrm{Na}_2$($1 ^3Σ_u^+$), $\mathrm{K}_2$($1 ^1Σ_g^+$), $\mathrm{K}_2$($1 ^3Σ_u^+$) and $\mathrm{Rb}_2$($1 ^1Σ_g^+$), the alignment dynamics are well-described by a 2D rotor model. We ascribe this to a significant confinement of the internuclear axis of these dimers, induced by the orientation-dependent droplet-dimer interaction, to the tangential plane of their residence point on the droplet. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2502_14521 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Nonadiabatic laser-induced alignment dynamics of alkali dimers on the surface of a helium droplet Kristensen, Henrik H. Kranabetter, Lorenz Ghazaryan, Areg Schouder, Constant A. Hansen, Emil Jensen, Frank Zillich, Robert E. Lemeshko, Mikhail Stapelfeldt, Henrik Atomic and Molecular Clusters Alkali dimers, $\mathrm{Ak}_2$, located on the surface of a helium nanodroplet, are set into rotation through the polarizability interaction with a nonresonant 1-ps-long laser pulse. The time-dependent degree of alignment is recorded using femtosecond-probe-pulse-induced Coulomb explosion into a pair of $\mathrm{Ak}^+$ fragment ions. The results, obtained for $\mathrm{Na}_2$, $\mathrm{K}_2$, and $\mathrm{Rb}_2$ in both the ground state $1 ^1Σ_g^+$ and the lowest-lying triplet state $1 ^3Σ_u^+$, exhibit distinct, periodic revivals with a gradually decreasing amplitude. The dynamics differ from that expected for dimers had they behaved as free rotors. Numerically, we solve the time-dependent rotational Schrödinger equation, including an effective mean-field potential to describe the interaction between the dimer and the droplet. The experimental and simulated alignment dynamics agree well and their comparison enables us to determine the effective rotational constants of the alkali dimers with the exception of $\mathrm{Rb}_2$($1 ^3Σ_u^+$) that only exhibits a prompt alignment peak but no subsequent revivals. For $\mathrm{Na}_2$($1 ^3Σ_u^+$), $\mathrm{K}_2$($1 ^1Σ_g^+$), $\mathrm{K}_2$($1 ^3Σ_u^+$) and $\mathrm{Rb}_2$($1 ^1Σ_g^+$), the alignment dynamics are well-described by a 2D rotor model. We ascribe this to a significant confinement of the internuclear axis of these dimers, induced by the orientation-dependent droplet-dimer interaction, to the tangential plane of their residence point on the droplet. |
| title | Nonadiabatic laser-induced alignment dynamics of alkali dimers on the surface of a helium droplet |
| topic | Atomic and Molecular Clusters |
| url | https://arxiv.org/abs/2502.14521 |