Dissociative recombination of vibrationally excited<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">HD</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>: State-selective experimental investigation

Amitay, Zohar; Baer, A.; Dahan, M.; Levin, J. J.; Vager, Z.; Zajfman, D.; Knöll, L.; Lange, Michael; Schwalm, D.; Wester, Roland; Wolf, A.; Schneider, I. F.; Suzor-Weiner, A.

doi:10.1103/physreva.60.3769

Cited by 69 publications

(55 citation statements)

References 40 publications

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“…For low collision energies the rate decreases with increasing vibrational excitation. This decrease is less than a factor of 2 and excludes vibrational specific rates that differ by an order of magnitude, as is found 61 for HD ϩ . The calculated thermal rate coefficient, ␣(O 2 ϩ ), at 300 K corresponding to the coolest population P1 is 2.0•10 Ϫ7 cm 3 s Ϫ1 and decreases to 1.5•10 Ϫ7 cm 3 s Ϫ1 for the hottest population P5.…”

Section: Discussionmentioning

confidence: 51%

Vibrationally resolved rate coefficients and branching fractions in the dissociative recombination of O2+

Petrignani

Zande

Cosby

et al. 2004

The Journal of Chemical Physics

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We have studied the dissociative recombination of the first three vibrational levels of O 2 ϩ in its electronic ground X 2 ⌸ g state. Absolute rate coefficients, cross sections, quantum yields and branching fractions have been determined in a merged-beam experiment in the heavy-ion storage ring, CRYRING, employing fragment imaging for the reaction dynamics. We present the absolute total rate coefficients as function of collision energies up to 0.4 eV for five different vibrational populations of the ion beam, as well as the partial ͑vibrationally resolved͒ rate coefficients and the branching fractions near 0 eV collision energy for the vibrational levels vϭ0, 1, and 2. The vibrational populations used were produced in a modified electron impact ion source, which has been calibrated using Cs-O 2 ϩ dissociative charge transfer reactions. The measurements indicate that at low collision energies, the total rate coefficient is weakly dependent on the vibrational excitation. The calculated thermal rate coefficient at 300 K decreases upon vibrational excitation. The partial rate coefficients as well as the partial branching fractions are found to be strongly dependent on the vibrational level. The partial rate coefficient is the fastest for vϭ0 and goes down by a factor of two or more for vϭ1 and 2. The O( 1 S) quantum yield, linked to the green airglow, increases strongly upon increasing vibrational level. The effects of the dissociative recombination reactions and super elastic collisions on the vibrational populations are discussed.

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Section: Discussionmentioning

confidence: 51%

Vibrationally resolved rate coefficients and branching fractions in the dissociative recombination of O2+

Petrignani

Zande

Cosby

et al. 2004

The Journal of Chemical Physics

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“…3. The basic experimental procedures have been described in detail earlier regarding merged electron and ion beam experiments in general [32], DR of molecular ions [33,34], and Coulomb explosion imaging [35,36].…”

Section: A Ion Beam and Detector Setupmentioning

confidence: 99%

“…(17) The kinetic energy distribution after Coulomb explosion for an ensemble of ions in a given vibrational state v has a characteristic form P v (Ẽ k ) [36] that reflects the distribution of nuclear positions and momenta in this state as well as the fragment scattering in the foil, broadening the distribution by ∼20%. For an ensemble of ions in several vibrational states the normalized kinetic energy distribution after Coulomb explosion…”

Section: Coulomb Explosion Diagnosticsmentioning

confidence: 99%

Dissociative recombination and low-energy inelastic electron collisions of the helium dimer ion

et al. 2005

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The dissociative recombination (DR) of 3 He 4 He + has been investigated at the heavy-ion Test Storage Ring (TSR) in Heidelberg by observing neutral products from electron-ion collisions in a merged beams configuration at relative energies from near-zero (thermal electron energy about 10 meV) up to 40 eV. After storage and electron cooling for 35 s, an effective DR rate coefficient at nearzero energy of 3 × 10 −9 cm 3 s −1 is found. The temporal evolution of the neutral product rates and fragment imaging spectra reveals that the populations of vibrational levels in the stored ion beam are non-thermal with fractions of ∼0.1-1% in excited levels up to at least v = 4, having a significant effect on the observed DR signals. With a pump-probe-type technique using DR fragment imaging while switching the properties of the electron beam, the vibrational excitation of the ions is found to originate mostly from ion collisions with the residual gas. Also, the temporal evolution of the DR signals suggests that a strong electron induced rotational cooling occurs in the vibrational ground state, reaching a rotational temperature near or below 300 K. From the absolute rate coefficient and the shape of the fragment imaging spectrum observed under stationary conditions, the DR rate coefficient from the vibrational ground state is determined; converted to a thermal electron gas at 300 K it amounts to (3.3 ± 0.9) × 10 −10 cm 3 s −1 . The corresponding branching ratios from v = 0 to the atomic final states are found to be (3.7 ± 1.2)% for 1s2s 3 S, (37.4 ± 4.0)% for 1s2s 1 S, (58.6 ± 5.2)% for 1s2p 3 P , and (2.9 ± 3.0)% for 1s2p 1 P . A DR rate coefficient in the range of 2 × 10 −7 cm 3 s −1 or above is inferred for vibrational levels v = 3 and higher. As a function of the collision energy, the measured DR rate coefficient displays a structure around 0.2 eV. At higher energies, it has one smooth peak around 7.3 eV and a highly structured appearance at 15-40 eV. The small size of the observed effective DR rate coefficient at near-zero energy indicates that the electron induced rotational cooling is due to inelastic electron-ion collisions and not due to selective depletion of rotational levels by DR.

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“…A similar continuum discretization scheme was used by Takagi in the DE study of hydrogen molecular ion [19,20] and in the DR computation of HeH + below 1 eV [34]. Takagi treated the channels associated with the discretized levels as dissociation ones.…”

Section: Basic Equationsmentioning

confidence: 99%

“…We mention the DR measurements for vibrationally cold hydrogen molecular ions performed in the ion storage ring experiments [17][18][19][20][21][22][23][24][25][26].…”

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confidence: 99%

Dissociative excitation of HD +, D 2+, and DT + by electron impact

Duca

Fifirig

2009

Open Physics

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Abstract:In the framework of the Multi-Channel Quantum Defect Theory (MQDT), a theoretical study of the dissociative excitation is presented. Numerical results for the dissociative excitation cross sections of HD + , D + 2 , and DT + with electrons of energy between 2 and 12 eV are reported. The contribution of the vibrational continua of the two lowest electronic states as explicit ionization channels has been considered. Within a quasi-diabatic representation of the molecular electronic states, the Born expansion of second order is done in the K-matrix evaluation.

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Dissociative recombination of vibrationally excitedHD+: State-selective experimental investigation

Cited by 69 publications

References 40 publications

Vibrationally resolved rate coefficients and branching fractions in the dissociative recombination of O2+

Vibrationally resolved rate coefficients and branching fractions in the dissociative recombination of O2+

Dissociative recombination and low-energy inelastic electron collisions of the helium dimer ion

Dissociative excitation of HD +, D 2+, and DT + by electron impact

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