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Ritter ME, DeSouza SA, Ogden HM, Michael TJ, Mullin AS. Transient IR spectroscopy of optically centrifuged CO 2 (R186-R282) and collision dynamics for the J = 244-282 states. Faraday Discuss 2024. [PMID: 38766993 DOI: 10.1039/d3fd00179b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Collisions of optically centrifuged CO2 molecules with J = 244-282 (Erot = 22 800-30 300 cm-1) are investigated with high-resolution transient IR absorption spectroscopy to reveal collisional and orientational phenomena of molecules with hyper-thermal rotational energies. The optical centrifuge is a non-resonant optical excitation technique that uses ultrafast, 800 nm chirped pulses to drive molecules to extreme rotational states through sequential Raman transitions. The extent of rotational excitation is controlled by tuning the optical bandwidth of the excitation pulses. Frequencies of 30 R-branch ν3 fundamental IR probe transitions are measured for the J = 186-282 states of CO2, expanding beyond previously reported IR transitions up to J = 128. The optically centrifuged molecules have oriented angular momentum and unidirectional rotation. Polarization-sensitive transient IR absorption of individual rotational states of optically centrifuged molecules and their collision products reveals information about collisional energy transfer, relaxation kinetics, and dynamics of rotation-to-translation energy transfer. The transient IR probe also measures the extent of polarization anisotropy. Rotational energy transfer for lower energy molecules is discussed in terms of statistical models and a comparison highlights the role of increasing energy gap with J and angular momentum of the optically centrifuged molecules.
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Affiliation(s)
- Michael E Ritter
- Department of Chemistry and Biochemistry, University of Maryland College Park, College Park, Maryland 20742, USA.
| | - Simone A DeSouza
- Department of Chemistry and Biochemistry, University of Maryland College Park, College Park, Maryland 20742, USA.
| | - Hannah M Ogden
- Department of Chemistry and Biochemistry, University of Maryland College Park, College Park, Maryland 20742, USA.
| | - Tara J Michael
- Department of Chemistry and Biochemistry, University of Maryland College Park, College Park, Maryland 20742, USA.
| | - Amy S Mullin
- Department of Chemistry and Biochemistry, University of Maryland College Park, College Park, Maryland 20742, USA.
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Venkataramanababu S, Li A, Antonov IO, Dragan JB, Stollenwerk PR, Guo H, Odom BC. Enhancing reactivity of SiO + ions by controlled excitation to extreme rotational states. Nat Commun 2023; 14:4446. [PMID: 37488115 PMCID: PMC10366143 DOI: 10.1038/s41467-023-40135-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Accepted: 07/11/2023] [Indexed: 07/26/2023] Open
Abstract
Optical pumping of molecules provides unique opportunities for control of chemical reactions at a wide range of rotational energies. This work reports a chemical reaction with extreme rotational excitation of a reactant and its kinetic characterization. We investigate the chemical reactivity for the hydrogen abstraction reaction SiO+ + H2 → SiOH+ + H in an ion trap. The SiO+ cations are prepared in a narrow rotational state distribution, including super-rotor states with rotational quantum number (j) as high as 170, using a broad-band optical pumping method. We show that the super-rotor states of SiO+ substantially enhance the reaction rate, a trend reproduced by complementary theoretical studies. We reveal the mechanism for the rotational enhancement of the reactivity to be a strong coupling of the SiO+ rotational mode with the reaction coordinate at the transition state on the dominant dynamical pathway.
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Affiliation(s)
- Sruthi Venkataramanababu
- Applied Physics Program, Northwestern University, Evanston, 60208, IL, USA
- Department of Physics, Northwestern University, Evanston, 60208, IL, USA
| | - Anyang Li
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi'an, 710127, P. R. China.
| | - Ivan O Antonov
- Lebedev Physical Institute, Samara, 443011, Russian Federation
| | - James B Dragan
- Department of Physics, Northwestern University, Evanston, 60208, IL, USA
| | | | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, 87131, NM, USA
| | - Brian C Odom
- Department of Physics, Northwestern University, Evanston, 60208, IL, USA.
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Chen TY, Steinmetz SA, Patterson BD, Jasper AW, Kliewer CJ. Direct observation of coherence transfer and rotational-to-vibrational energy exchange in optically centrifuged CO 2 super-rotors. Nat Commun 2023; 14:3227. [PMID: 37270647 DOI: 10.1038/s41467-023-38873-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 05/18/2023] [Indexed: 06/05/2023] Open
Abstract
Optical centrifuges are laser-based molecular traps that can rotationally accelerate molecules to energies rivalling or exceeding molecular bond energies. Here we report time and frequency-resolved ultrafast coherent Raman measurements of optically centrifuged CO2 at 380 Torr spun to energies beyond its bond dissociation energy of 5.5 eV (Jmax = 364, Erot = 6.14 eV, Erot/kB = 71, 200 K). The entire rotational ladder from J = 24 to J = 364 was resolved simultaneously which enabled a more accurate measurement of the centrifugal distortion constants for CO2. Remarkably, coherence transfer was directly observed, and time-resolved, during the field-free relaxation of the trap as rotational energy flowed into bending-mode vibrational excitation. Vibrationally excited CO2 (ν2 > 3) was observed in the time-resolved spectra to populate after 3 mean collision times as a result of rotational-to-vibrational (R-V) energy transfer. Trajectory simulations show an optimal range of J for R-V energy transfer. Dephasing rates for molecules rotating up to 5.5 times during one collision were quantified. Very slow decays of the vibrational hot band rotational coherences suggest that they are sustained by coherence transfer and line mixing.
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Affiliation(s)
- Timothy Y Chen
- Sandia National Laboratories, Livermore, 94550, CA, USA
- Applied Materials, Inc., Santa Clara, 95051, CA, USA
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Laskowski MR, Michael TJ, Ogden HM, Alexander MH, Mullin AS. Rotational energy transfer kinetics of optically centrifuged CO molecules investigated through transient IR spectroscopy and master equation simulations. Faraday Discuss 2022; 238:87-102. [DOI: 10.1039/d2fd00068g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A combined experimental and theoretical study of quantum state-resolved rotational energy transfer kinetics of optically centrifuged CO molecules is presented. In the experiments, inverted rotational distributions of CO in rotational...
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Amani P, Milner AA, Milner V. Selective rotational control in mixtures of molecular super-rotors. J Chem Phys 2021; 155:124201. [PMID: 34598555 DOI: 10.1063/5.0062051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We demonstrate experimentally a method of all-optical selective rotational control in gas mixtures. Using an optical centrifuge-an intense laser pulse whose linear polarization rotates at an accelerated rate, we simultaneously excite two different molecular species to two different rotational frequencies of choice. The new level of control is achieved by shaping the centrifuge spectrum according to the rotational spectra of the centrifuged molecules. The shaped optical centrifuge releases one molecular species earlier than the other, therefore separating their target rotational frequencies and corresponding rotational states. The technique is applicable to molecules with non-overlapping rotational spectra in the frequency range of interest and will expand the utility of rotational control in the studies of the effects of molecular rotation on collisions and chemical reactions.
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Affiliation(s)
- Pedram Amani
- Department of Physics & Astronomy, The University of British Columbia, Vancouver, British Columbia V6T-1Z1, Canada
| | - Alexander A Milner
- Department of Physics & Astronomy, The University of British Columbia, Vancouver, British Columbia V6T-1Z1, Canada
| | - Valery Milner
- Department of Physics & Astronomy, The University of British Columbia, Vancouver, British Columbia V6T-1Z1, Canada
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Michael TJ, Ogden HM, Mullin AS. State-resolved rotational distributions and collision dynamics of CO molecules made in a tunable optical centrifuge. J Chem Phys 2021; 154:134307. [PMID: 33832253 DOI: 10.1063/5.0038372] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
State-resolved distributions and collision dynamics of optically centrifuged CO molecules with orientated angular momentum are investigated by probing the CO J = 29-80 rotational levels using high-resolution transient IR absorption spectroscopy. An optical centrifuge with tunable bandwidth is used to control the extent of rotational excitation in the sample. The rotational distributions are inverted with a maximum population in J = 62. Rotational levels with J > 62 have populations that correlate with the intensity profile of the optical trap. The full bandwidth trap excites CO up to the J = 80 level, while J = 67 is the highest level observed in the reduced bandwidth trap. Polarization-sensitive transient spectroscopy shows that the initial orientational anisotropy is r = 0.8 for levels with J ≥ 55, while anisotropy values are near r = 0.4 for levels with J < 50. The rotational distribution for J > 50 is broadened slightly by collisions, consistent with small |ΔJ| propensity rules for rotational energy transfer. Doppler-broadened line profiles show that the J = 60-80 levels have translational temperatures near Ttrans = 300 K and that these temperatures remain constant for as much as 24 gas kinetic collisions. Doppler linewidths for levels with J < 60 are broadened by non-resonant rotation-to-translation energy transfer. Kinetic analysis of transient signals shows that collisions with thermal bath molecules are the predominant relaxation pathway.
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Affiliation(s)
- Tara J Michael
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
| | - Hannah M Ogden
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
| | - Amy S Mullin
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
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Ogden HM, Michael TJ, Murray MJ, Liu Q, Toro C, Mullin AS. The effect of CO rotation from shaped pulse polarization on reactions that form C2. Phys Chem Chem Phys 2019; 21:14103-14110. [DOI: 10.1039/c8cp06917d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The effect of CO rotational energy on bimolecular reactions to form electronically excited C2 is reported here.
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Affiliation(s)
- Hannah M. Ogden
- Department of Chemistry and Biochemistry
- University of Maryland
- College Park
- USA
| | - Tara J. Michael
- Department of Chemistry and Biochemistry
- University of Maryland
- College Park
- USA
| | | | - Qingnan Liu
- National Institute of Standards and Technology
- Gaithersburg
- USA
| | - Carlos Toro
- Department of Chemistry and Biochemistry
- University of Maryland
- College Park
- USA
| | - Amy S. Mullin
- Department of Chemistry and Biochemistry
- University of Maryland
- College Park
- USA
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Murray MJ, Ogden HM, Mullin AS. Importance of rotational adiabaticity in collisions of CO2 super rotors with Ar and He. J Chem Phys 2018; 148:084310. [DOI: 10.1063/1.5009440] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Matthew J. Murray
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
| | - Hannah M. Ogden
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
| | - Amy S. Mullin
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
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