High‐resolution Photofragment Translational Spectroscopy using Rydberg Tagging Methods

Ashfold, Michael N. R.; King, Graeme A.; Nix, Michael G. D.; Oliver, Thomas A. A.

doi:10.1002/9780470749593.hrs092

Cited by 3 publications

(4 citation statements)

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“…Because of the rapid increase of the lifetimes with increasing values of n and m , and of the Rydbergstate spectral density with n, the overall effect is a preferential population of Rydberg states having longer lifetimes, and thus a reduction of the decay rate with time. The observation of transitions between Rydberg states induced by thermal radiation and/or collisions, even at low temperatures, indicates that such transitions must be included in the analysis of the present results and may play a role in other experiments relying on the long lifetimes of Rydberg states, such as H-atom photofragment-translational-spectroscopic experiments [41] and experiments on antihydrogen at CERN [17,42].…”

Section: Resultsmentioning

confidence: 96%

Radiative and collisional processes in translationally cold samples of hydrogen Rydberg atoms studied in an electrostatic trap

Seiler¹,

Agner²,

Pillet³

et al. 2016

J. Phys. B: At. Mol. Opt. Phys.

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Supersonic beams of hydrogen atoms, prepared selectively in Rydberg-Stark states of principal quantum number n in the range between 25 and 35, have been deflected by 90 ○ , decelerated and loaded into off-axis electric traps at initial densities of ≈ 10 6 atoms/cm −3 and translational temperatures of 150 mK. The ability to confine the atoms spatially was exploited to study their decay by radiative and collisional processes. The evolution of the population of trapped atoms was measured for several milliseconds in dependence of the principal quantum number of the initially prepared states, the initial Rydberg-atom density in the trap, and the temperature of the environment of the trap, which could be varied between 7.5 K and 300 K using a cryorefrigerator. At room temperature, the population of trapped Rydberg atoms was found to decay faster than expected on the basis of their natural lifetimes, primarily because of absorption and emission stimulated by the thermal radiation field. At the lowest temperatures investigated experimentally, the decay was found to be multiexponential, with an initial rate scaling as n −4 and corresponding closely to the natural lifetimes of the initially prepared Rydberg-Stark states. The decay rate was found to continually decrease over time and to reach an almost n-independent rate of more than (1 ms) −1 after 3 ms. To analyze the experimentally observed decay of the populations of trapped atoms, numerical simulations were performed which included all radiative processes, i.e., spontaneous emission as well as absorption and emission stimulated by the thermal radiation. These simulations, however, systematically underestimated the population of trapped atoms observed after several milliseconds by almost two orders of magnitude, although they reliably predicted the decay rates of the remaining atoms in the trap. The calculations revealed that the atoms that remain in the trap for the longest times have larger absolute values of the magnetic quantum number m than the optically prepared RydbergStark states, and this observation led to the conclusion that a much more efficient mechanism than a purely radiative one must exist to induce transitions to Rydberg-Stark states of higher m values. While searching for such a mechanism, we discovered that resonant dipole-dipole collisions between Rydberg atoms in the trap represent an extremely efficient way of inducing transitions to states of higher m values. The efficiency of the mechanism is a consequence of the almost perfectly linear nature of the Stark effect at the moderate field strengths used to trap the atoms, which permits cascades of transitions between entire networks of near-degenerate Rydberg-atom-pair states. To include such cascades of resonant dipole-dipole transitions in the numerical simulations, we have generalized the two-state Förster-type collision model used to describe resonant collisions in ultracold Rydberg gases to a multi-state situation. It is only when considering the combined effects of collisional and radiative pr...

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Section: Resultsmentioning

confidence: 96%

Radiative and collisional processes in translationally cold samples of hydrogen Rydberg atoms studied in an electrostatic trap

Seiler¹,

Agner²,

Pillet³

et al. 2016

J. Phys. B: At. Mol. Opt. Phys.

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“…Such dynamical behaviour is well known for excited state H atom dissociation. 35 Although the present experiment was not designed to characterize ion fragments, our arrangement still allowed the H -product to be imaged, albeit offset from the 8 centre along the propagation axis of the ion beam because of the perpendicular VMI arrangement and the mass (time-of-flight) difference between an electron and H -.To velocity-map H -, we extended the imaging acquisition gate on the MCP from 100 ns to 1 s to account for the much longer time-of-flight of H -compared with photoelectrons. image centre and the H -image centre (assuming that the photoelectron centre is the true zerovelocity centre of the spectrometer).…”

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confidence: 99%

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confidence: 99%

Charged Particle Imaging of the Deprotonated Octatrienoic Acid Anion: Evidence for a Photoinduced Cyclization Reaction

West

Bull

Verlet

2016

J. Phys. Chem. Lett.

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. (2016) 'Charged particle imaging of the deprotonated octatrienoic acid anion : evidence for a photoinduced cyclization reaction.', The journal of physical chemistry letters., 7 (22). pp. 4635-4640. Further information on publisher's website:https://doi.org/10.1021/acs.jpclett.6b02302Publisher's copyright statement:This document is the Accepted Manuscript version of a Published Work that appeared in nal form in The journal of physical chemistry letters, copyright c American Chemical Society after peer review and technical editing by the publisher. To access the nal edited and published work see https://doi.org/10.1021/acs.jpclett.6b02302Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. (Figure 1) was generated by electrospray ionisation, mass-selected and intersected with laser pulses (~5 ns duration) at 4.13 eV (300 nm) or 4.66 eV (266 nm) at the centre of a perpendicular velocity-map imaging (VMI) spectrometer. 23,24 The VMI spectrometer has been optimised to perform photoelectron spectroscopy by gating the imaging detector with ~100 ns gate pulse and reconstructing the raw image. 25 However, the same perpendicular VMI spectrometer can also be used to image other charged species, such as H -. Supporting ground electronic structure calculations were performed at the G4 5 level of theory and resonance energetics computed at multi-state XCMQDPT2 level of theory. 26,27 The photoelectron spectra of [C7H9-CO2] -taken at hv = 4.13 eV and 4.66 eV are shown in Figure 1(a) and (b), respectively. The photoelectron spectra are dominated by a peak at low electron kinetic energy, eKE, which is generally indicative of the indirect electron loss process of thermionic emission. 15,20,28,29 In addition to this low eKE peak, there are several minor features at higher eKE. In the hν = 4.13 eV spectrum, the low eKE peak has a shoulder that extends up to ~1.4 eV and a weak feature that peaks at eKE ~ 2.5 eV as indicated by the asterisk in Figure 1(a). The photoelectron spectrum at hν = 4.66 eV, shown in Figure 1(b), is broadly similar, although the shoulder to the dominating low eKE peak is larger than at hν = 4.13 eV and extends to eKE ~1.9 eV, which is consistent with a direct photodetachment process. The hν = 4.66 eV spectrum does not, however, show the clear peak around eKE ~ 2.5 eV (or at eKE ~ 3.0 eV taking into account the additional photon energy).In addition to the peak at eKE ~ 2.5 eV in the hν = 4.13 eV photoelectron spectrum, a discernible peak is present at eKE ~ 3.3 eV, as indicated by the arrow in Fig...

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“…The solid curves associated with each set of data in Figure 9 are the result of a Monte-Carlo calculation of the trap decay rate including the effects of blackbody radiation and spontaneous emission and capture well the main features of the decay. An understanding of the effect of 300 K blackbody radiation on the lifetimes of Rydberg states of atomic hydrogen is of value in the interpretation of H atom photofragmentation translational spectra recorded by Rydberg tagging 145 .…”

Section: Determination Of Excited State Lifetimesmentioning

confidence: 99%

Deceleration of supersonic beams using inhomogeneous electric and magnetic fields

Hogan

Motsch

Merkt

2011

Phys. Chem. Chem. Phys.

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High‐resolution Photofragment Translational Spectroscopy using Rydberg Tagging Methods

Cited by 3 publications

References 50 publications

Radiative and collisional processes in translationally cold samples of hydrogen Rydberg atoms studied in an electrostatic trap

Radiative and collisional processes in translationally cold samples of hydrogen Rydberg atoms studied in an electrostatic trap

Charged Particle Imaging of the Deprotonated Octatrienoic Acid Anion: Evidence for a Photoinduced Cyclization Reaction

Deceleration of supersonic beams using inhomogeneous electric and magnetic fields

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