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Nötzold M, Wild R, Lochmann C, Rahim T, Melath SP, Dulitz K, Mant B, Franz J, Gianturco FA, Wester R. Vibrational Quenching of Optically Pumped Carbon Dimer Anions. PHYSICAL REVIEW LETTERS 2023; 131:183002. [PMID: 37977634 DOI: 10.1103/physrevlett.131.183002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Revised: 08/08/2023] [Accepted: 09/25/2023] [Indexed: 11/19/2023]
Abstract
Careful control of quantum states is a gateway to research in many areas of science such as quantum information, quantum-controlled chemistry, and astrophysical processes. Precise optical control of molecular ions remains a challenge due to the scarcity of suitable level schemes, and direct laser cooling has not yet been achieved for either positive or negative molecular ions. Using a cryogenic wire trap, we show how the internal quantum states of C_{2}^{-} anions can be manipulated using optical pumping and inelastic quenching collisions with H_{2} gas. We obtained optical pumping efficiencies of about 96% into the first vibrational level of C_{2}^{-} and determined the absolute inelastic rate coefficient from v=1 to 0 to be k_{q}=(3.2±0.2_{stat}±1.3_{sys})×10^{-13} cm^{3}/s at 20(3) K, over 3 orders of magnitude smaller than the capture limit. Reduced-dimensional quantum scattering calculations yield a small rate coefficient as well, but significantly larger than the experimental value. Using optical pumping and inelastic collisions, we also realized fluorescence imaging of negative molecular ions. Our work demonstrates high control of a cold ensemble of C_{2}^{-}, providing a solid foundation for future work on laser cooling of molecular ions.
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Affiliation(s)
- Markus Nötzold
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Robert Wild
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Christine Lochmann
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Tanja Rahim
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Sruthi Purushu Melath
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Katrin Dulitz
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Barry Mant
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Jan Franz
- Faculty of Applied Physics and Mathematics and Advanced Materials Center, Gdańsk University of Technology, 80-233 Gdańsk, Poland
| | - Francesco A Gianturco
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
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González-Sánchez L, Yurtsever E, Mant BP, Wester R, Gianturco FA. Collision-driven state-changing efficiency of different buffer gases in cold traps: He( 1S), Ar( 1S) and p-H 2( 1Σ) on trapped CN -( 1Σ). Phys Chem Chem Phys 2021; 23:7703-7713. [PMID: 32804174 DOI: 10.1039/d0cp03440a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We employ potential energy surfaces (PES) from ab initio quantum chemistry methods to describe the interaction of the CN-(1Σ) molecule, one of the small anions often studied at low temperatures, with other possible gases which can be employed as buffer in cold ion traps: the He and Ar atoms and the p-H2 molecule. These PESs are used to calculate from quantum multichannel dynamics the corresponding state-changing rate constants between the populated rotational states of the anion, the latter being in its electronic and vibrational ground states. The different cross sections for the collision-driven quenching and excitation processes at low temperatures are compared and further used to model CN- cooling (de-excitation) efficiency under different trap conditions. The interplay of potential coupling strength and mass-scaling effects is discussed to explain the differences of behaviour among the buffer gases. The advantages of being able to perform collisional cooling at higher trap temperatures when using Ar and p-H2 as buffer gases are also discussed.
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Affiliation(s)
- Lola González-Sánchez
- Departamento de Química Física, University of Salamanca, Plaza de los Caídos sn, 37008 Salamanca, Spain
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Gianturco FA, Giri K, González-Sánchez L, Yurtsever E, Sathyamurthy N, Wester R. Energy-transfer quantum dynamics of HeH + with He atoms: Rotationally inelastic cross sections and rate coefficients. J Chem Phys 2021; 154:054311. [PMID: 33557566 DOI: 10.1063/5.0040018] [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
Two different ab initio potential energy surfaces are employed to investigate the efficiency of the rotational excitation channels for the polar molecular ion HeH+ interacting with He atoms. We further use them to investigate the quantum dynamics of both the proton-exchange reaction and the purely rotational inelastic collisions over a broad range of temperatures. In current modeling studies, this cation is considered to be one of the possible cooling sources under early universe conditions after the recombination era and has recently been found to exist in the interstellar medium. The results from the present calculations are able to show the large efficiency of the state-changing channels involving rotational states of this cation. In fact, we find them to be similar in size and behavior to the inelastic and reaction rate coefficients obtained in previous studies, where H atoms were employed as projectiles. The same rotational excitation processes, occurring when free electrons are the collision partners of this cation, are also compared with the present findings. The relative importance of the reactive, proton-exchange channel and the purely inelastic channels is also analyzed and discussed. The rotational de-excitation processes are also investigated for the cooling kinetics of the present cation under cold trap conditions with He as the buffer gas. The implications of the present results for setting up more comprehensive numerical models to describe the chemical evolution networks in different environments are briefly discussed.
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Affiliation(s)
- F A Gianturco
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - K Giri
- Department of Computational Sciences, Central University of Punjab, Bathinda 151001, India
| | - L González-Sánchez
- Departamento de Química Física, University of Salamanca, Plaza de los Caídos sn, 37008 Salamanca, Spain
| | - E Yurtsever
- Department of Chemistry, Koç University, Rumelifeneriyolu, Sariyer TR, 34450 Istanbul, Turkey
| | - N Sathyamurthy
- Indian Institute of Science Education and Research Mohali, SAS Nagar, Manauli 140306, India
| | - R Wester
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
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Geistlinger K, Fischer M, Spieler S, Remmers L, Duensing F, Dahlmann F, Endres E, Wester R. A sub-4 Kelvin radio frequency linear multipole wire trap. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:023204. [PMID: 33648123 DOI: 10.1063/5.0040866] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 01/22/2021] [Indexed: 06/12/2023]
Abstract
A linear cryogenic 16-pole wire ion trap has been developed and constructed for cryogenic ion spectroscopy at temperatures below 4 K. The trap is temperature-variable, can be operated with different buffer gases, and offers large optical access perpendicular to the ion beam direction. The housing geometry enables temperature measurement during radio frequency operation. The effective trapping potential of the wire-based radio frequency trap is described and compared to conventional multipole ion trap designs. Furthermore, time-of-flight mass spectra of multiple helium tagged protonated glycine ions that are extracted from the trap are presented, which prove very low ion temperatures and suitable conditions for sensitive spectroscopy.
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Affiliation(s)
- Katharina Geistlinger
- Universität Innsbruck, Institut für Ionenphysik und Angewandte Physik, Technikerstraße 25/3, 6020 Innsbruck, Austria
| | - Moritz Fischer
- Universität Innsbruck, Institut für Ionenphysik und Angewandte Physik, Technikerstraße 25/3, 6020 Innsbruck, Austria
| | - Steffen Spieler
- Universität Innsbruck, Institut für Ionenphysik und Angewandte Physik, Technikerstraße 25/3, 6020 Innsbruck, Austria
| | - Lena Remmers
- Universität Innsbruck, Institut für Ionenphysik und Angewandte Physik, Technikerstraße 25/3, 6020 Innsbruck, Austria
| | - Felix Duensing
- Universität Innsbruck, Institut für Ionenphysik und Angewandte Physik, Technikerstraße 25/3, 6020 Innsbruck, Austria
| | - Franziska Dahlmann
- Universität Innsbruck, Institut für Ionenphysik und Angewandte Physik, Technikerstraße 25/3, 6020 Innsbruck, Austria
| | - Eric Endres
- Universität Innsbruck, Institut für Ionenphysik und Angewandte Physik, Technikerstraße 25/3, 6020 Innsbruck, Austria
| | - Roland Wester
- Universität Innsbruck, Institut für Ionenphysik und Angewandte Physik, Technikerstraße 25/3, 6020 Innsbruck, Austria
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Franz J, Mant BP, González-Sánchez L, Wester R, Gianturco FA. Rotational state-changing collisions of C 2H - and C 2N - anions with He under interstellar and cold ion trap conditions: A computational comparison. J Chem Phys 2020; 152:234303. [PMID: 32571047 DOI: 10.1063/5.0011585] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
We present an extensive range of quantum calculations for the state-changing rotational dynamics involving two simple molecular anions that are expected to play some role in the evolutionary analysis of chemical networks in the interstellar environments, C2H- (X1Σ+) and C2N- (X3Σ-), but for which inelastic rates are only known for C2H-. The same systems are also of direct interest in modeling selective photo-detachment experiments in cold ion traps where the He atoms function as the chief buffer gas at the low trap temperatures. This study employs accurate, ab initio calculations of the interaction potential energy surfaces for these anions, treated as rigid rotors, and the He atom to obtain a wide range of state-changing quantum cross sections and rates at temperatures up to about 100 K. The results are analyzed and compared for the two systems to show differences and similarities between their rates of state-changing dynamics.
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Affiliation(s)
- Jan Franz
- Department of Theoretical Physics and Quantum Informatics, Faculty of Applied Physics and Mathematics, Gdańsk University of Technology, ul. Narutowicza 11/12, 80-233 Gdańsk, Poland
| | - Barry P Mant
- Institute for Ion Physics and Applied Physics, University of Innsbruck, Technikerstr. 25/3, 6020 Innsbruck, Austria
| | - Lola González-Sánchez
- Departamento de Química Física, University of Salamanca, Plaza de los Caídos s/n, 37008 Salamanca, Spain
| | - Roland Wester
- Institute for Ion Physics and Applied Physics, University of Innsbruck, Technikerstr. 25/3, 6020 Innsbruck, Austria
| | - Franco A Gianturco
- Institute for Ion Physics and Applied Physics, University of Innsbruck, Technikerstr. 25/3, 6020 Innsbruck, Austria
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Gianturco FA, González-Sánchez L, Mant BP, Wester R. Modeling state-selective photodetachment in cold ion traps: Rotational state "crowding" in small anions. J Chem Phys 2019; 151:144304. [PMID: 31615254 DOI: 10.1063/1.5123218] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Using accurate ab initio calculations of the interaction forces, we employ a quantum mechanical description of the collisional state-changing processes that occur in a cold ion trap with He as a buffer gas. We generate the corresponding inelastic rates for rotational transitions involving three simple molecular anions OH-(1Σ), MgH-(1Σ), and C2H-(1Σ) colliding with the helium atoms of the trap. We show that the rotational constants of these molecular anions are such that within the low-temperature regimes of a cold ion trap (up to about 50 K), a different proportion of molecular states are significantly populated when loading helium as a buffer gas in the trap. By varying the trap operating conditions, population equilibrium at the relevant range of temperatures is reached within different time scales. In the modeling of the photodetachment experiments, we analyze the effects of varying the chosen values for photodetachment rates as well as the laser photon fluxes. Additionally, the changing of the collision dynamics under different buffer gas densities is examined and the best operating conditions, for the different anions, for yielding higher populations of specific rotational states within the ion traps are extracted. The present modeling thus illustrates possible preparation of the trap conditions for carrying out more efficiently state-selected experiments with the trapped anions.
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Affiliation(s)
- F A Gianturco
- Institut fuer Ionenphysik und Angewandte Physik, Universitaet Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - L González-Sánchez
- Departamento de Química Física, University of Salamanca, Plaza de los Caídos sn, 37008 Salamanca, Spain
| | - B P Mant
- Institut fuer Ionenphysik und Angewandte Physik, Universitaet Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - R Wester
- Institut fuer Ionenphysik und Angewandte Physik, Universitaet Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
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González-Sánchez L, Gómez-Carrasco S, Santadaría AM, Wester R, Gianturco FA. Collisional Quantum Dynamics for MgH - ( 1Σ +) With He as a Buffer Gas: Ionic State-Changing Reactions in Cold Traps. Front Chem 2019; 7:64. [PMID: 30809520 PMCID: PMC6379277 DOI: 10.3389/fchem.2019.00064] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 01/23/2019] [Indexed: 11/17/2022] Open
Abstract
We present in this paper a detailed theoretical and computational analysis of the quantum inelastic dynamics involving the lower rotational levels of the MgH− (X1Σ+) molecular anion in collision with He atoms which provide the buffer gas in a cold trap. The interaction potential between the molecular partner and the He (1S) gaseous atoms is obtained from accurate quantum chemical calculations at the post-Hartree-Fock level as described in this paper. The spatial features and the interaction strength of the present potential energy surface (PES) are analyzed in detail and in comparison with similar, earlier results involving the MgH+ (1Σ) cation interacting with He atoms. The quantum, multichannel dynamics is then carried out using the newly obtained PES and the final inelastic rats constants, over the range of temperatures which are expected to be present in a cold ion trap experiment, are obtained to generate the multichannel kinetics of population changes observed for the molecular ion during the collisional cooling process. The rotational populations finally achieved at specific temperatures are linked to state-selective laser photo-detachment experiments to be carried out in our laboratory.All intermediate steps of the quantum modeling are also compared with the behavior of the corresponding MgH+ cation in the trap and the marked differences which exist between the collisional dynamics of the two systems are dicussed and explained. The feasibility of the present anion to be involved in state-selective photo-detachment experiments is fully analyzed and suggestions are made for the best performing conditions to be selected during trap experiments.
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Affiliation(s)
| | | | | | - Roland Wester
- Department of Physics, Institut für Ionenphysik und Angewandte Physik, Universitaet Innsbruck, Innsbruck, Austria
| | - Francesco A Gianturco
- Department of Physics, Institut für Ionenphysik und Angewandte Physik, Universitaet Innsbruck, Innsbruck, Austria
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Lakhmanskaya O, Simpson M, Murauer S, Kokoouline V, Wester R. Photodetachment spectroscopy of cold trapped NH2- near threshold. J Chem Phys 2018; 149:104302. [PMID: 30219014 DOI: 10.1063/1.5042621] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have studied photodetachment of the amidogen anion NH2- as a function of photon energy near the detachment threshold. The detachment spectrum is obtained over the energy range of 6190-6355 cm-1 from the loss rate of the anions from a cryogenic radiofrequency multipole ion trap. By modeling all accessible rotational state-to-state photodetachment transitions, we can assign rotational state-specific thresholds to the measured spectrum. In this way, we have determined the electron affinity of NH2 to be 6224 ± 1 cm-1.
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Affiliation(s)
- Olga Lakhmanskaya
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Malcolm Simpson
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Simon Murauer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Viatcheslav Kokoouline
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
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