Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

The Journal of Physical Chemistry Letters

Experimental Observation of the Autler–Townes Splitting in Polyatomic Molecules

Junggil Kim, Jean Sun Lim, Heung‐Ryoul Noh, Sang Kyu Kim

Published Jul 29, 2020• 14 citations
Publisher

Abstract

Autler–Townes (AT) splitting has been experimentally observed in the optical transition between the zero-point levels of S 1 and S 0 for supersonically cooled 2-methoxythiophenol, 2-fluorothiophenol, and 2-chlorothiophenol. This is the first experimental observation of the light-dressed quantum states of polyatomic molecules ( N > 3) in the electronic transition. In the resonance-enhanced ionization process involving the optically coupled states, if Rabi cycling is ensured within the nanosecond laser pulse, AT splitting is clearly observed for the open system for which the excited-state lifetime is shorter than hundreds of picoseconds. Semiclassical optical Bloch equations and a dressed-atom approach based on the three-level atomic model describe the experiment quite well, giving deep insights into the light–matter interaction in polyatomic molecular systems.

DOI
10.1021/acs.jpclett.0c01918

Related papers

INVESTIGATION OF AUTLER-TOWNES SPLITTING AND AC STARK EFFECT IN A LITHIUM MOLECULE BY MULTI-PHOTON SPECTROSCOPY

Jianbing Qi, Frank C. Spano, Guenadiy Lazarov +4 more

In recent years, coherent effects in atomic and molecular systems have been studied extensively, especially in several new classes of effects, such as lasing without inversion (LWI), electromagnetically induced transparency (EIT), coherent population trapping (CPT), AC Stark effect and Autler-Townes (AT) splitting in multilevel systems. The AC stark effect and Autler-Townes splitting in molecules have only been investigated recently. We demonstrate AC stark effect and Autler-Townes (AT) splitting in a lithium molecule using cw multi-photon spectroscopy. The excited upper level of the $G^{1}\\Pi_{g}$ is prepared by the optical-optical double resonance (OODR) excitation. The OODR line is split in the presence of a third coupling laser, which couples the upper level to an another intermediate level when the coupling laser is on or near resonance transition. The AT line shape consists of the superposition of $|M_{J}|$ components which have been resolved for $G^{1}\\Pi_{g}(v=12, J=3,f)$. We find that the AT splittingis linearly proportional to $|M_{J}|$, which allows the excitation of molecules with a selected $|M_{J}|$ level. The AC Stark shift of the OODR line is observed when the coupling laser is detuned from the resonance transition.

•Jan 1, 1999•0 citations

Autler-Townes splitting of ultracold cesium Rydberg atoms

Xue Yong-Mei, Hao Li-Ping, Jiao Yue-Chun +4 more

Autler-Townes (A-T) splitting, known as an AC Stark effect, shows a change of an absorption/emission spectral line of a probe beam when an oscillating field is tuned in resonance with the atomic or molecular transition. The A-T splitting is observed in different three-level atoms and widely investigated in a vapor cell and in a magneto-optical trap (MOT). The A-T splitting plays an important role in the atom-based microwave electric-field measurements where a cascade three-level system involving Rydberg state is adopted. In this work, an A-T splitting is observed in an ultracold cesium Rydberg gas, which is cooled down to about 100 pK and center density is about 1010 cm-3 in a conventional MOT by using the laser cooling technology. We present the A-T spectrum in a ladder three-level atomic system involving a 34D5/2 Rydberg state. The cesium ground state (6S1/2), excited state (6P3/2) and Rydberg state (34D5/2) constitute a Rydberg three-level system. A coupling laser, locked to the Rydberg transition by using a Rydberg electromagnetically induced transparency signal that is obtained from a cesium room-temperature vapor cell, couples 6P3/2 (F'=5) 34D5/2 Rydberg transition. A weak probe laser, stabilized to a ground-state transition by using a polarization spectroscopy, is swept, covering the transition 6S1/2 (F=4) 6P3/2 (F'=5) with a double-passed acousto-optic modulator. The probe and coupling lasers are counter-propagated through the MOT center. The power of probe light is 200 pW, corresponding Rabi frequency p=21.05 MHz. During the experiment, 50 s after turning off the trapping laser, both the coupling and probe beams are switched on and last 100 s. The A-T spectrum as a function of the probe detuning is detected with a single-photon counter module detector. We use Gaussian multiple peak fitting to obtain the positions of the A-T peaks and the A-T splitting. The measured A-T splitting is proportional to the Rabi frequency of the coupling light. We numerically solve the density matrix equations to obtain the A-T spectrum, and the calculations reproduce A-T spectra well. The measured A-T splitting shows good agreement with the theoretical calculation for Rabi frequency of the coupling light c29 MHz. The A-T splitting is less than the calculation for the case of c29 MHz, the deviation is mainly attributed to the increased dephasing rate induced by the strong interaction between Rydberg atoms, whose number increases with the coupling laser Rabi frequency. In this work, the adopted method for the cascade three-level system involving Rydberg state is also suitable for -and V-type cases.

Acta Physica Sinica•Jan 1, 2017•3 citations

Autler—Townes doublet in the absorption spectra for the transition between excited states of cold cesium atoms

Qiangbing Liang, Baodong Yang, Jianfeng Yang +2 more

Autler—Townes splitting in absorption spectra of the excited states 6 2 P 3/2 –8 2 S 1/2 of cold cesium atoms confined in a magneto-optical trap has been observed. Experimental data of the Autler—Townes splitting fit well to the dressed-atom theory, by which the fact of the cold atoms dressed by cooling/trapping laser beams is revealed. The results of the theoretical fitting with experiment not only told us the effective Rabi frequency cold atoms experienced, but also could be used for measuring the probability amplitudes of the dressed states.

Chinese Physics B•Nov 1, 2010•5 citations

Controlling Autler–Townes Splitting of the K 2 Molecule with Quantum Light

Zhaopeng Sun, Xiaoxiao Long, Yunquan Liu

Autler–Townes splitting (ATS) is a hallmark phenomenon of strong light–matter interaction, in which the resonant photoelectron energy spectrum splits into distinct peaks when driven by a strong electromagnetic field. We investigate the Autler–Townes Splitting (ATS) in K 2 molecules with quantum light. The triple splitting structures originating from three-photon ionization are analyzed under different types of driving fields, including bright squeezed vacuum (BSV), phase-squeezed coherent (PSC) light and amplitude-squeezed coherent (ASC) light by numerically solving the time-dependent Schrödinger equation. Compared with the results with the coherent-state (classical) light drive, we show that the ATS dynamics is sensitive with the squeezing parameter of quantum light, leading to modifications of the subband structures and splitting magnitudes. In particular, a BSV pulse exhibits a higher splitting efficiency than a classical pulse of the same mean intensity. This work has implications on ultrafast coherent control of molecular reactions with quantum light.

The Journal of Physical Chemistry Letters•May 29, 2026•1 citation

Direct observation of two-photon-resonance Autler-Townes splitting of atomic sodium

Wankai Li, Yixuan Wang, Xing Li +3 more

A two-photon resonance in the sodium atom $3s\text{\ensuremath{-}}4s$ transition is investigated in the strong coupling regime with photoelectron momentum imaging techniques. The kinetic energies of the ionized electron map out the eigenenergies of the dressed states and emerge as the Autler-Townes (AT) splitting, which is proportional to the laser intensity due to the two-photon nature. The partial wave analysis of the angular distribution of the photoelectrons reveals the relative phase shift from dressed states which is related to the attosecond ionization time delays. The phase shift between the two electron wave packets produced from AT splitting are attributed to the combination of the Coulomb phase and the quantum defect phase.

Physical Review A•Jun 2, 2025•6 citations

Autler–Townes splitting and the AC Stark effect in nonpolar molecules: Prospects for all-optical alignment

A. M. Lyyra, J. Qi, F. C. Spano

This paper describes an extension of the familiar coherence effects from atomic systems to the molecular regime. Such effects are inherent in the interaction of multiple laser fields with molecular systems. We have observed Autler–Townes splitting and the AC Stark shift in diatomic Lithium using the continuous wave all-optical triple resonance (AOTR) techniques. By using the Autler–Townes effect, we have partially resolved the magnetic sublevels of a molecular rovibrational level in a Doppler broadened sample, allowing all-optical alignment of the angular momentum in excited states of nonpolar molecules. The Autler–Townes effect in a molecular system extends the rovibrational state selectivity of the AOTR excitation technique to magnetic sublevels. PACS Nos.: 33.40tf, 42.50Hz

Canadian Journal of Physics•Jan 1, 2001•1 citation
Autler–Townes (AT) splitting has been experimentally observed in the optical transition between the zero-point levels of S 1 and S 0 for supersonically cooled 2-methoxythiophenol, 2-fluorothiophenol, and 2-chlorothiophenol. This is the first experimental observation of the light-dressed quantum states of polyatomic molecules ( N > 3) in the electronic transition. In the resonance-enhanced ionization process involving the optically coupled states, if Rabi cycling is ensured within the nanosecond laser pulse, AT splitting is clearly observed for the open system for which the excited-state lifetime is shorter than hundreds of picoseconds. Semiclassical optical Bloch equations and a dressed-atom approach based on the three-level atomic model describe the experiment quite well, giving deep insights into the light–matter interaction in polyatomic molecular systems.
In recent years, coherent effects in atomic and molecular systems have been studied extensively, especially in several new classes of effects, such as lasing without inversion (LWI), electromagnetically induced transparency (EIT), coherent population trapping (CPT), AC Stark effect and Autler-Townes (AT) splitting in multilevel systems. The AC stark effect and Autler-Townes splitting in molecules have only been investigated recently. We demonstrate AC stark effect and Autler-Townes (AT) splitting in a lithium molecule using cw multi-photon spectroscopy. The excited upper level of the G1PigG^{1}\\Pi_{g}G1Pig​ is prepared by the optical-optical double resonance (OODR) excitation. The OODR line is split in the presence of a third coupling laser, which couples the upper level to an another intermediate level when the coupling laser is on or near resonance transition. The AT line shape consists of the superposition of ∣MJ∣|M_{J}|∣MJ​∣ components which have been resolved for G1Pig(v=12,J=3,f)G^{1}\\Pi_{g}(v=12, J=3,f)G1Pig​(v=12,J=3,f). We find that the AT splittingis linearly proportional to ∣MJ∣|M_{J}|∣MJ​∣, which allows the excitation of molecules with a selected ∣MJ∣|M_{J}|∣MJ​∣ level. The AC Stark shift of the OODR line is observed when the coupling laser is detuned from the resonance transition.
Autler-Townes (A-T) splitting, known as an AC Stark effect, shows a change of an absorption/emission spectral line of a probe beam when an oscillating field is tuned in resonance with the atomic or molecular transition. The A-T splitting is observed in different three-level atoms and widely investigated in a vapor cell and in a magneto-optical trap (MOT). The A-T splitting plays an important role in the atom-based microwave electric-field measurements where a cascade three-level system involving Rydberg state is adopted. In this work, an A-T splitting is observed in an ultracold cesium Rydberg gas, which is cooled down to about 100 pK and center density is about 1010 cm-3 in a conventional MOT by using the laser cooling technology. We present the A-T spectrum in a ladder three-level atomic system involving a 34D5/2 Rydberg state. The cesium ground state (6S1/2), excited state (6P3/2) and Rydberg state (34D5/2) constitute a Rydberg three-level system. A coupling laser, locked to the Rydberg transition by using a Rydberg electromagnetically induced transparency signal that is obtained from a cesium room-temperature vapor cell, couples 6P3/2 (F'=5) 34D5/2 Rydberg transition. A weak probe laser, stabilized to a ground-state transition by using a polarization spectroscopy, is swept, covering the transition 6S1/2 (F=4) 6P3/2 (F'=5) with a double-passed acousto-optic modulator. The probe and coupling lasers are counter-propagated through the MOT center. The power of probe light is 200 pW, corresponding Rabi frequency p=21.05 MHz. During the experiment, 50 s after turning off the trapping laser, both the coupling and probe beams are switched on and last 100 s. The A-T spectrum as a function of the probe detuning is detected with a single-photon counter module detector. We use Gaussian multiple peak fitting to obtain the positions of the A-T peaks and the A-T splitting. The measured A-T splitting is proportional to the Rabi frequency of the coupling light. We numerically solve the density matrix equations to obtain the A-T spectrum, and the calculations reproduce A-T spectra well. The measured A-T splitting shows good agreement with the theoretical calculation for Rabi frequency of the coupling light c29 MHz. The A-T splitting is less than the calculation for the case of c29 MHz, the deviation is mainly attributed to the increased dephasing rate induced by the strong interaction between Rydberg atoms, whose number increases with the coupling laser Rabi frequency. In this work, the adopted method for the cascade three-level system involving Rydberg state is also suitable for -and V-type cases.
Autler—Townes splitting in absorption spectra of the excited states 6 2 P 3/2 –8 2 S 1/2 of cold cesium atoms confined in a magneto-optical trap has been observed. Experimental data of the Autler—Townes splitting fit well to the dressed-atom theory, by which the fact of the cold atoms dressed by cooling/trapping laser beams is revealed. The results of the theoretical fitting with experiment not only told us the effective Rabi frequency cold atoms experienced, but also could be used for measuring the probability amplitudes of the dressed states.
Autler–Townes splitting (ATS) is a hallmark phenomenon of strong light–matter interaction, in which the resonant photoelectron energy spectrum splits into distinct peaks when driven by a strong electromagnetic field. We investigate the Autler–Townes Splitting (ATS) in K 2 molecules with quantum light. The triple splitting structures originating from three-photon ionization are analyzed under different types of driving fields, including bright squeezed vacuum (BSV), phase-squeezed coherent (PSC) light and amplitude-squeezed coherent (ASC) light by numerically solving the time-dependent Schrödinger equation. Compared with the results with the coherent-state (classical) light drive, we show that the ATS dynamics is sensitive with the squeezing parameter of quantum light, leading to modifications of the subband structures and splitting magnitudes. In particular, a BSV pulse exhibits a higher splitting efficiency than a classical pulse of the same mean intensity. This work has implications on ultrafast coherent control of molecular reactions with quantum light.
A two-photon resonance in the sodium atom $3s\text{\ensuremath{-}}4s$ transition is investigated in the strong coupling regime with photoelectron momentum imaging techniques. The kinetic energies of the ionized electron map out the eigenenergies of the dressed states and emerge as the Autler-Townes (AT) splitting, which is proportional to the laser intensity due to the two-photon nature. The partial wave analysis of the angular distribution of the photoelectrons reveals the relative phase shift from dressed states which is related to the attosecond ionization time delays. The phase shift between the two electron wave packets produced from AT splitting are attributed to the combination of the Coulomb phase and the quantum defect phase.
This paper describes an extension of the familiar coherence effects from atomic systems to the molecular regime. Such effects are inherent in the interaction of multiple laser fields with molecular systems. We have observed Autler–Townes splitting and the AC Stark shift in diatomic Lithium using the continuous wave all-optical triple resonance (AOTR) techniques. By using the Autler–Townes effect, we have partially resolved the magnetic sublevels of a molecular rovibrational level in a Doppler broadened sample, allowing all-optical alignment of the angular momentum in excited states of nonpolar molecules. The Autler–Townes effect in a molecular system extends the rovibrational state selectivity of the AOTR excitation technique to magnetic sublevels. PACS Nos.: 33.40tf, 42.50Hz