Physical Review A

Anomalies in the rotational spectra of Sr 86 ultralong-range Rydberg molecule dimers

C. Wang, Y. Lu, Ang Li, S. K. Kanungo, T. C. Killian, F. B. Dunning, S. Yoshida

Published May 9, 2025• 2 citations

Abstract

Anomalies in the rotational structure of $^{86}\mathrm{Sr}$ $^{3}S_{1}$ dimer ultralong-range Rydberg molecules created in a cold strontium gas by two-photon excitation via the intermediate $5s5p$ $^{3}P_{1}$ state are reported. Measurements reveal that the distribution of product rotational states is sensitive to intermediate state detuning. Comparative studies using $^{84}\mathrm{Sr}$ $^{1}S_{0}$ and $^{3}S_{1}$, and $^{86}\mathrm{Sr}$ $^{1}S_{0}$ dimers display no similar behavior, indicating that the observed behavior is peculiar to $^{86}\mathrm{Sr}$ triplet dimers. While we have no definitive hypothesis as to the physical mechanism responsible for this behavior, possible explanations might involve the very different scattering lengths for $^{84}\mathrm{Sr}$ and $^{86}\mathrm{Sr}$, or the interchange of spin and rotational angular momentum.

DOI: 10.1103/physreva.111.052811

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Anomalies in the rotational spectra of $^{86}$Sr ULRRM dimers

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Physical Review A

Anomalies in the rotational spectra of Sr 86 ultralong-range Rydberg molecule dimers

C. Wang, Y. Lu, Ang Li, S. K. Kanungo, T. C. Killian, F. B. Dunning, S. Yoshida

Published May 9, 2025• 2 citations

Publisher

Abstract

Anomalies in the rotational structure of

^{86}\mathrm{Sr}

^{3}S_{1}

dimer ultralong-range Rydberg molecules created in a cold strontium gas by two-photon excitation via the intermediate

5s5p

^{3}P_{1}

state are reported. Measurements reveal that the distribution of product rotational states is sensitive to intermediate state detuning. Comparative studies using

^{84}\mathrm{Sr}

^{1}S_{0}

and

^{3}S_{1}

, and

^{86}\mathrm{Sr}

^{1}S_{0}

dimers display no similar behavior, indicating that the observed behavior is peculiar to

^{86}\mathrm{Sr}

triplet dimers. While we have no definitive hypothesis as to the physical mechanism responsible for this behavior, possible explanations might involve the very different scattering lengths for

^{84}\mathrm{Sr}

and

^{86}\mathrm{Sr}

, or the interchange of spin and rotational angular momentum.

DOI: 10.1103/physreva.111.052811

Related papers

Anomalies in the rotational spectra of $^{86}$ Sr ULRRM dimersAnomalies in the rotational spectra of $^{86}$Sr ULRRM dimers

C. Wang, Lu, Y., Li, A. +4 more

Anomalies in the rotational structure of $^{86}$ Sr $^3S_1$ dimer ultralong-range Rydberg molecules (ULRRMs) created in a cold strontium gas by two-photon excitation via the intermediate $5s5p~^3P_1$ state are reported. Measurements reveal that the distribution of product rotational states is sensitive to intermediate state detuning. Comparative studies using $^{84}$ Sr $^1S_0$ and $^3S_1$ , and $^{86}$ Sr $^1S_0$ dimers display no similar behavior, indicating that the observed behavior is peculiar to $^{86}$ Sr triplet dimers. While we have no definitive hypothesis as to the physical mechanism responsible for this behavior, possible explanations might involve the very different scattering lengths for $^{84}$ Sr and $^{86}$ Sr, or the interchange of spin and rotational angular momentum.Anomalies in the rotational structure of $^{86}$Sr $^3S_1$ dimer ultralong-range Rydberg molecules (ULRRMs) created in a cold strontium gas by two-photon excitation via the intermediate $5s5p~^3P_1$ state are reported. Measurements reveal that the distribution of product rotational states is sensitive to intermediate state detuning. Comparative studies using $^{84}$Sr $^1S_0$ and $^3S_1$, and $^{86}$Sr $^1S_0$ dimers display no similar behavior, indicating that the observed behavior is peculiar to $^{86}$Sr triplet dimers. While we have no definitive hypothesis as to the physical mechanism responsible for this behavior, possible explanations might involve the very different scattering lengths for $^{84}$Sr and $^{86}$Sr, or the interchange of spin and rotational angular momentum.

arXiv:2501.14303Jan 24, 20250 citations

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Spectroscopic measurements of the rotational distribution of $^{84}\mathrm{Sr}$ and $^{86}\mathrm{Sr}\phantom{\rule{4pt}{0ex}}\phantom{\rule{0.16em}{0ex}}5sns{\phantom{\rule{0.16em}{0ex}}}^{1}{S}_{0}$ ultralong-range Rydberg molecular dimers created via photoassociation in a cold gas are reported. The dimers are produced by two-photon excitation via the $5s5p$ $^{1}P_{1}$ intermediate state. The use of singlet states permits detailed study of the roles that the initial atom-atom interaction, photon momentum transfer during Rydberg excitation, and sample temperature play in determining the spectral line shape and final dimer rotational distribution. The results are in good agreement with the predictions of a model that includes these effects. The present work further highlights the sensitivity of ultralong-range Rydberg molecule formation to the state of the initial cold gas.Spectroscopic measurements of the rotational distribution of $^{84}\mathrm{Sr}$ and $^{86}\mathrm{Sr}\phantom{\rule{4pt}{0ex}}\phantom{\rule{0.16em}{0ex}}5sns{\phantom{\rule{0.16em}{0ex}}}^{1}{S}_{0}$ ultralong-range Rydberg molecular dimers created via photoassociation in a cold gas are reported. The dimers are produced by two-photon excitation via the $5s5p$ $^{1}P_{1}$ intermediate state. The use of singlet states permits detailed study of the roles that the initial atom-atom interaction, photon momentum transfer during Rydberg excitation, and sample temperature play in determining the spectral line shape and final dimer rotational distribution. The results are in good agreement with the predictions of a model that includes these effects. The present work further highlights the sensitivity of ultralong-range Rydberg molecule formation to the state of the initial cold gas.

arXiv:2406.08671Physical Review ASep 6, 20244 citations

Resolving rotationally excited states of ultralong-range Rydberg molecules

Y. Lu, J. D. Whalen, S. K. Kanungo +4 more

We report experimental observations of the rotational structure in photoassociative spectroscopy of ultralong-range Rydberg molecules (ULRRMs) in an ultracold gas of $^{86}\mathrm{Sr}$ . ULRRM spectroscopy probes scattering wave functions at much larger internuclear separations than photoassociative spectroscopy of low-lying electronic states. At such separations photon recoil momentum can lead to the transfer of significant angular momentum to the Rydberg molecule, evidence of which is provided through the distribution of excited rotational states. The visibility of the rotational structure is enhanced because, for collisions between ground-state $^{86}\mathrm{Sr}$ atoms, the large, near-resonant s-wave scattering length approaches the size of the ULRRM. Similar enhancement is not seen for $^{84}\mathrm{Sr}$ , which has a much smaller scattering length. Results are interpreted with the aid of a theory that accounts for the recoil momentum associated with photoexcitation and the large $s$ -wave scattering length in the entrance channel. While the observed rotational splittings and the qualitative trends in the relative intensities of the spectral features are well described by theory, the effects of recoil momentum are more prominent in the measured data than in the theory.We report experimental observations of the rotational structure in photoassociative spectroscopy of ultralong-range Rydberg molecules (ULRRMs) in an ultracold gas of $^{86}\mathrm{Sr}$. ULRRM spectroscopy probes scattering wave functions at much larger internuclear separations than photoassociative spectroscopy of low-lying electronic states. At such separations photon recoil momentum can lead to the transfer of significant angular momentum to the Rydberg molecule, evidence of which is provided through the distribution of excited rotational states. The visibility of the rotational structure is enhanced because, for collisions between ground-state $^{86}\mathrm{Sr}$ atoms, the large, near-resonant s-wave scattering length approaches the size of the ULRRM. Similar enhancement is not seen for $^{84}\mathrm{Sr}$, which has a much smaller scattering length. Results are interpreted with the aid of a theory that accounts for the recoil momentum associated with photoexcitation and the large $s$-wave scattering length in the entrance channel. While the observed rotational splittings and the qualitative trends in the relative intensities of the spectral features are well described by theory, the effects of recoil momentum are more prominent in the measured data than in the theory.

Physical Review AAug 16, 20228 citations

Photoassociation of Sr 84 n 1 D 2 ultralong-range Rydberg dimers

C. Wang, Ang Li, S. K. Kanungo +3 more

Measurements of the production of 5 s n d 1 D 2 – 5 s 2 1 S 0 ultralong-range Rydberg dimers through photoassocation in an ultracold Sr 84 atomic gas are reported. The molecular potential associated with the Rydberg D state is anisotropic and the molecular states are characterized by the vibrational quantum number ν and the total angular momentum K ⃗ = L ⃗ + N ⃗ , where L ⃗ and N ⃗ are the electronic orbital angular momentum and rotational angular momentum, respectively. The measured molecular binding energies agree reasonably well with theoretical predictions. Additionally, the electron-atom scattering leads to broader line shapes in the photoassociation spectrum than might be expected simply from the angular momentum of the initial colliding cold-atom pairs.Measurements of the production of 5 s n d 1 D 2 – 5 s 2 1 S 0 ultralong-range Rydberg dimers through photoassocation in an ultracold Sr 84 atomic gas are reported. The molecular potential associated with the Rydberg D state is anisotropic and the molecular states are characterized by the vibrational quantum number ν and the total angular momentum K ⃗ = L ⃗ + N ⃗ , where L ⃗ and N ⃗ are the electronic orbital angular momentum and rotational angular momentum, respectively. The measured molecular binding energies agree reasonably well with theoretical predictions. Additionally, the electron-atom scattering leads to broader line shapes in the photoassociation spectrum than might be expected simply from the angular momentum of the initial colliding cold-atom pairs.

Physical Review AApr 7, 20261 citation

Creation of vibrationally-excited ultralong-range Rydberg molecules in polarized and unpolarized cold gases of 87 Sr

R Ding, S K Kanungo, J D Whalen +4 more

Abstract Photoexcitation rates for creation of ultralong-range Rydberg molecules with 31 ≲ n ≲ 41 in both ground and excited vibrational levels in cold ( T ∼ 900 nK) gases of polarized and unpolarized 87 Sr are presented. The measured production rates of the ν = 0, 1 and 2 vibrational levels reveal rather different n dependences which are analyzed by evaluating the Franck–Condon factors associated with excitation of the different vibrational levels and molecular rotational states. In particular, for gases of spin-polarized fermions, only Rydberg dimers with odd rotational quantum numbers are excited due to the requirement that their wave functions be anti-symmetric with respect to exchange. The data also demonstrate that measurements of the formation of vibrationally-excited ν = 1 molecules can furnish a probe of pair correlations over intermediate length scales.Abstract Photoexcitation rates for creation of ultralong-range Rydberg molecules with 31 ≲ n ≲ 41 in both ground and excited vibrational levels in cold ( T ∼ 900 nK) gases of polarized and unpolarized 87 Sr are presented. The measured production rates of the ν = 0, 1 and 2 vibrational levels reveal rather different n dependences which are analyzed by evaluating the Franck–Condon factors associated with excitation of the different vibrational levels and molecular rotational states. In particular, for gases of spin-polarized fermions, only Rydberg dimers with odd rotational quantum numbers are excited due to the requirement that their wave functions be anti-symmetric with respect to exchange. The data also demonstrate that measurements of the formation of vibrationally-excited ν = 1 molecules can furnish a probe of pair correlations over intermediate length scales.

arXiv:1909.04634Journal of Physics B Atomic Molecular and Optical PhysicsDec 4, 201910 citations

Effect of an applied magnetic field on Sr 84 n 1 D 2 ultralong-range Rydberg dimers

S. Yoshida, C. Wang, Ang Li +3 more

Photoassociation of 5 s n d 1 D 2 − 5 s 2 1 S 0 ultralong-range Rydberg dimers from an ultracold Sr 84 atomic gas in a magnetic field is studied. In the absence of magnetic fields, the electronic wave function is aligned along the rotating molecular axis through electron-atom scattering. With increasing magnetic field strength, the symmetry axis of the electron wave function becomes determined by the applied field. While the ground-state atom has no spin or net charge to interact directly with the magnetic field, the dimer wave function in the limit of strong magnetic field becomes aligned along the applied field. Photoassociation spectra show that with increasing field, an increasing number of rovibrational states are excited, indicating strong coupling between rotational states within the Rydberg dimer.Photoassociation of 5 s n d 1 D 2 − 5 s 2 1 S 0 ultralong-range Rydberg dimers from an ultracold Sr 84 atomic gas in a magnetic field is studied. In the absence of magnetic fields, the electronic wave function is aligned along the rotating molecular axis through electron-atom scattering. With increasing magnetic field strength, the symmetry axis of the electron wave function becomes determined by the applied field. While the ground-state atom has no spin or net charge to interact directly with the magnetic field, the dimer wave function in the limit of strong magnetic field becomes aligned along the applied field. Photoassociation spectra show that with increasing field, an increasing number of rovibrational states are excited, indicating strong coupling between rotational states within the Rydberg dimer.

Physical Review AJul 22, 20260 citations

Anomalies in the rotational structure of

^{86}\mathrm{Sr}

^{3}S_{1}

dimer ultralong-range Rydberg molecules created in a cold strontium gas by two-photon excitation via the intermediate

5s5p

^{3}P_{1}

state are reported. Measurements reveal that the distribution of product rotational states is sensitive to intermediate state detuning. Comparative studies using

^{84}\mathrm{Sr}

^{1}S_{0}

and

^{3}S_{1}

, and

^{86}\mathrm{Sr}

^{1}S_{0}

dimers display no similar behavior, indicating that the observed behavior is peculiar to

^{86}\mathrm{Sr}

triplet dimers. While we have no definitive hypothesis as to the physical mechanism responsible for this behavior, possible explanations might involve the very different scattering lengths for

^{84}\mathrm{Sr}

and

^{86}\mathrm{Sr}

, or the interchange of spin and rotational angular momentum.

Anomalies in the rotational spectra of

^{86}

Sr ULRRM dimers

Anomalies in the rotational structure of

^{86}

^3S_1

dimer ultralong-range Rydberg molecules (ULRRMs) created in a cold strontium gas by two-photon excitation via the intermediate

5s5p~^3P_1

state are reported. Measurements reveal that the distribution of product rotational states is sensitive to intermediate state detuning. Comparative studies using

^{84}

^1S_0

and

^3S_1

, and

^{86}

^1S_0

dimers display no similar behavior, indicating that the observed behavior is peculiar to

^{86}

Sr triplet dimers. While we have no definitive hypothesis as to the physical mechanism responsible for this behavior, possible explanations might involve the very different scattering lengths for

^{84}

Sr and

^{86}

Sr, or the interchange of spin and rotational angular momentum.

Spectroscopic measurements of the rotational distribution of

^{84}\mathrm{Sr}

and

^{86}\mathrm{Sr}\phantom{\rule{4pt}{0ex}}\phantom{\rule{0.16em}{0ex}}5sns{\phantom{\rule{0.16em}{0ex}}}^{1}{S}_{0}

ultralong-range Rydberg molecular dimers created via photoassociation in a cold gas are reported. The dimers are produced by two-photon excitation via the

5s5p

^{1}P_{1}

intermediate state. The use of singlet states permits detailed study of the roles that the initial atom-atom interaction, photon momentum transfer during Rydberg excitation, and sample temperature play in determining the spectral line shape and final dimer rotational distribution. The results are in good agreement with the predictions of a model that includes these effects. The present work further highlights the sensitivity of ultralong-range Rydberg molecule formation to the state of the initial cold gas.

We report experimental observations of the rotational structure in photoassociative spectroscopy of ultralong-range Rydberg molecules (ULRRMs) in an ultracold gas of

^{86}\mathrm{Sr}

. ULRRM spectroscopy probes scattering wave functions at much larger internuclear separations than photoassociative spectroscopy of low-lying electronic states. At such separations photon recoil momentum can lead to the transfer of significant angular momentum to the Rydberg molecule, evidence of which is provided through the distribution of excited rotational states. The visibility of the rotational structure is enhanced because, for collisions between ground-state

^{86}\mathrm{Sr}

atoms, the large, near-resonant s-wave scattering length approaches the size of the ULRRM. Similar enhancement is not seen for

^{84}\mathrm{Sr}

, which has a much smaller scattering length. Results are interpreted with the aid of a theory that accounts for the recoil momentum associated with photoexcitation and the large

s

-wave scattering length in the entrance channel. While the observed rotational splittings and the qualitative trends in the relative intensities of the spectral features are well described by theory, the effects of recoil momentum are more prominent in the measured data than in the theory.