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Guberman S.L.,Institute for Scientific Research | Orel A.E.,University of California at Davis
Journal of Physics: Conference Series | Year: 2011

In dissociative recombination (DR), a molecular ion captures an electron and falls apart. One might initially conclude that this process is relatively simple. However, a review of the DR literature over the past 60 years, since the pioneering papers of Sir David Bates [1], shows that the study of DR has proved to be highly challenging for both theorists and experimentalists. Both this challenge and the ubiquitous importance of the process have made its study rewarding, endlessly interesting, and full of surprises. DR is fundamentally the interaction of an electronic continuum with a vibrational continuum often connected by quasibound intermediate states. Autoionization in the first continuum competes with dissociation in the second. DR occurs at the total energy of an ion plus a free electron and is in the same region as vibrationally excited Rydberg states and other neutral superexcited states. All these states interact with each other prior to dissociation, forming a complex that controls the quantum yields of products. The complexity of the process has required both innovation and ingenuity on the part of both theorists and experimentalists. Over the years, it has become apparent that in order to compare theoretical and experimental results, the experiments must identify the electronic, vibrational and for low mass ions, the rotational state. The traditional disagreement between theoretical and experimental results has been due, in part, to the sensitivity of DR cross sections and rate constants to the state of the recombining ion. Great progress has been made in recent years in both flowing afterglow and storage ring experiments aimed at reducing this uncertainty. The latest advances and insights in theory and experiment were the topics of the Eighth International Conference on Dissociative Recombination held at the Granlibakken Lodge at Lake, Tahoe, California, 16-20 August 2010. The conference was part of a series of conferences on DR that started at Chateau Lake Louise, Alberta, Canada in May, 1988 [2] and was followed in May 1992 [3] at L'Abbaye de Saint Jacut de la Mer, Brittany, France, in May, 1995 [4] at Ein Gedi, Israel, in June 1999 [5] on the island of Nässlingen in the Stockholm archipelago, Sweden, in August, 2001 [6] at Chicago, USA, in July, 2004 [7] at the Alte Mälzerei, Mosbach, Germany and in July, 2007 [8] at the Resort d'Amelander Kaap on the island of Ameland, The Netherlands. All papers from the last two conferences and this conference are freely available at http://iopscience.iop. org/1742-6596. In keeping with the tradition of prior DR conferences, all papers in this volume have been refereed. Our thanks go to the referees for their efforts. Travel support for conference participants was provided by NSF grant ATM-0838061 and NASA grant NNX09AQ73G to SLG. We thank Priscilla Kujawski for proofreading the Dedication. Steven L GubermanAnn E OrelEditors Participants of the 8th International Conference on Dissociative Recombination: Theory, Experiments and Applications. 1. Stephen Pratt18. Randy Vane35. Robert Continetti 2. Chris Greene19. Claude Krantz36. Henrik Buhr 3. Bastiaan Braams20. Xavier Urbain37. Mats Larsson 4. Ed Grant21. Hidekazu Takagi38. Dirk Schwalm 5. Christian Nordhorn22. Brian Mitchell39. Evelyne Roueff 6. Steen Brønsted Nielsen23. Andreas Wolf40. Pascal Pernot 7. Dermot Madden24. Daren Stotler41. Stefan Rosén 8. Radek Plašil25. Slava Kokoouline42. Rainer Johnsen 9. Daniel Savin26. David Schultz43. Xiaohong Cai 10. Jonathan Tennyson27. Mourad Telmini44. Dan Haxton 11. Peet Hickman28. Ruth Malenda45. Åsa Larson 12. Michael Fogle29. Slim Chourou46. Dahbia Talbi 13. Waffeu Tamo Francois Oliver30. Petr Dohnal47. Ann Orel 14. Christian Jungen31. Julia Stützel48. Steven Guberman 15. Ilya Fabrikant32. Ioan Schneider49. Jane Fox 16. Wolf Geppert33. Nicholas Shuman50. Richard Thomas 17. Oldřich Novotný34. Holger Kreckel51. Fangfang Ruan.


Mauri G.,Institute for Scientific Research | Mauri G.,Italian National Cancer Institute | Fresa M.,Humanitas Gavazzeni Clinic | Ferraris M.,Humanitas Gavazzeni Clinic | And 5 more authors.
Minerva Cardioangiologica | Year: 2016

Critical hand ischemia (CHI) is a quite uncommon but highly disabling condition, generally caused by chronic occlusive arterial disease. For a correct approach to the endovascular treatment of these patients, good knowledge of the normal vascular anatomy and of the most frequently encountered vascular anatomical variations is of paramount importance. In the present paper a description of the normal vascular anatomy of the upper limb and of the most commonly encountered anatomical variations is provided, focusing on the implications for endovascular treatment of patients with CHI. Moreover, data of 151 patients with 172 critically ischemic hands treated at our institution between 2004 and 2016 are presented. © 2016 EDIZIONI MINERVA MEDICA.


Midey A.J.,Air Force Research Lab | Midey A.J.,Institute for Scientific Research | Midey A.J.,Excellims Corporation | Miller T.M.,Air Force Research Lab | And 5 more authors.
Analytical Chemistry | Year: 2010

Room temperature rate constants and product ion branching ratios have been measured for the reactions of numerous positive and negative ions with VX chemical warfare agent surrogates representing the amine (triethylamine) and organophosphonate (diethyl methythiomethylphosphonate (DEMTMP)) portions of VX. The measurements have been supplemented by theoretical calculations of the proton affinity, fluoride affinity, and ionization potential of VX and the simulants. The results show that many proton transfer reactions are rapid and that the proton affinity of VX is near the top of the scale. Many proton transfer agents should detect VX selectively and sensitively in chemical ionization mass spectrometers. Charge transfer with NO+ should also be sensitive and selective since the ionization potential of VX is small. The surrogate studies confirm these trends. Limits of detection for commercial and research grade CIMS instruments are estimated at 80 pptv and 5 ppqv, respectively. © 2010 American Chemical Society.


Guberman S.L.,Institute for Scientific Research
Journal of Chemical Physics | Year: 2013

Theoretical ab initio calculations are reported of the cross sections for dissociative recombination of the lowest four excited vibrational levels of N2+ at electron energies from 0.001 to 1.0 eV. Rydberg vibrational levels contributing to the cross section structures are identified as are dissociative channels contributing more than 10-16 cm2 to the total cross sections. In contrast to the prior study of v = 0 (S. L. Guberman, J. Chem. Phys. 137, 074309 (2012)), which showed 2 3Πu to be the dominant dissociative channel, 4 3Πu is dominant for v = 1. Both 2 and 4 3Πu are major routes for dissociative recombination from v = 2-4. Other routes including 23Σu+, 3 3Πu, 21Πu, 2 3Πg, 21Σg+, 11Δg, and b′1Σu+ are significant in narrow energy ranges. The results show that minor dissociative routes, included here for N2+, must be included in theoretical studies of other molecular ions (including the simplest ions H2+ and H3+) if cross section agreement is to be found with future high resolution dissociative recombination experiments. The calculated predissociation lifetimes of the Rydberg resonances are used in a detailed comparison to two prior storage ring experiments in order to determine if the prior assumption of isotropic atomic angular distributions at zero electron energy is justified. The prior experimental assumption of comparable cross sections for v = 0-3 is shown to be the case at zero but not at nonzero electron energies. Circumstances are identified in which indirect recombination may be visualized as a firefly effect. © 2013 AIP Publishing LLC.


Guberman S.L.,Institute for Scientific Research
Journal of Physics: Conference Series | Year: 2011

Since the proposal, sixty years ago, of the direct dissociative recombination (DR) mechanism by Bates, there have been many important theoretical advances, especially within the past 30 years. Space limitations preclude the review of all significant theoretical contributions. Instead, I comment upon a few selected developments. Highlights of the early scattering theory of DR and of the powerful Multichannel Quantum Defect Theory (MQDT) are discussed. Enhancements to the latter approach have included the addition of second and all order K matrices, ion rotational motion, Rydberg states with excited cores and spin-orbit coupling between Rydberg states. Also discussed are DR by Born-Oppenheimer breakdown, angular product distributions in diatomic DR and oscillations in DR cross sections.


Guberman S.L.,Institute for Scientific Research
Journal of Chemical Physics | Year: 2014

Dissociative recombination rate constants are reported with electron temperature dependent uncertainties for the lowest 5 vibrational levels of the N2 + ground state. The rate constants are determined from ab initio calculations of potential curves, electronic widths, quantum defects, and cross sections. At 100 K electron temperature, the rate constants overlap with the exception of the third vibrational level. At and above 300 K, the rate constants for excited vibrational levels are significantly smaller than that for the ground level. It is shown that any experimentally determined total rate constant at 300 K electron temperature that is smaller than 2.0 × 10-7 cm3/s is likely to be for ions that have a substantially excited vibrational population. Using the vibrational level specific rate constants, the total rate constant is in very good agreement with that for an excited vibrational distribution found in a storage ring experiment. It is also shown that a prior analysis of a laser induced fluorescence experiment is quantitatively flawed due to the need to account for reactions with unknown rate constants. Two prior calculations of the dissociative recombination rate constant are shown to be inconsistent with the cross sections upon which they are based. The rate constants calculated here contribute to the resolution of a 30 year old disagreement between modeled and observed N2 + ionospheric densities. © 2014 AIP Publishing LLC.


Guberman S.L.,Institute for Scientific Research
Journal of Chemical Physics | Year: 2012

Comprehensive theoretical calculations are reported for the dissociative recombination of the lowest vibrational level of the N2+ ground state. Fourteen dissociative channels, 21 electron capture channels, and 48 Rydberg series including Rydberg states having the first excited state of the ion as core are described for electron energies up to 1.0 eV. The calculation of potential curves, electron capture and predissociation widths, cross sections and rate constants are described. The cross sections and rate constants are calculated using Multichannel Quantum Defect Theory which allows for efficient handling of the Rydberg series. The most important dissociative channel is 2 3Π u followed by 4 3Π u. Dissociative states that do not cross the ion within the ground vibrational level turning points play a significant role in determining the cross section structure and at isolated energies can be more important than states having a favorable crossing. By accounting for autoionization, the interactions between resonances, between dissociative states, and between resonances and dissociative states it is found that the cross section can be viewed as a complex dissociative recombination spectrum in which resonances overlap and interfere. The detailed cross section exhibits a rapid variation in atomic quantum yields for small changes in the electron energy. A study of this rapid variation by future high resolution storage ring experiments is suggested. A least squares fit to the calculated rate constant from the ground vibrational level is 2.2+0.2-0.4×10-7×(Te/300)-0.40 cm 3/sec for electron temperatures, T e, between 100 and 3000 K and is in excellent agreement with experimentally derived values. © 2012 American Institute of Physics.


Guberman S.L.,Institute for Scientific Research
Journal of Physical Chemistry A | Year: 2013

Large scale ab initio calculations are reported for the diabatic 3Π, 1Π, 1Σ+, 1Δ, 3Σ+, and 3Δ valence states of CO that provide routes for the dissociative recombination of the ground electronic and vibrational state of CO+. The most important routes are 23Π, 33Π, 21Π, and D'1Σ+. For electron energies below 0.2961 eV, from the v = 0 ion level, the first two states can generate excited atoms, O(1D) and C(1D), but the last two states yield only ground state atoms. From v = 0, hot ground state atoms are generated at 0 eV from each of the four states with C and O having 1.67 and 1.25 eV of kinetic energy, respectively. The potential curves are compared to prior calculations and experiments. © 2013 American Chemical Society.


PubMed | Institute for Scientific Research
Type: Journal Article | Journal: The journal of physical chemistry. A | Year: 2014

Large scale ab initio calculations are reported for the diabatic (3), (1), (1)(+), (1), (3)(+), and (3) valence states of CO that provide routes for the dissociative recombination of the ground electronic and vibrational state of CO(+). The most important routes are 2(3), 3(3), 2(1), and D(1)(+). For electron energies below 0.2961 eV, from the v = 0 ion level, the first two states can generate excited atoms, O((1)D) and C((1)D), but the last two states yield only ground state atoms. From v = 0, hot ground state atoms are generated at 0 eV from each of the four states with C and O having 1.67 and 1.25 eV of kinetic energy, respectively. The potential curves are compared to prior calculations and experiments.


PubMed | Institute for Scientific Research
Type: Journal Article | Journal: The Journal of chemical physics | Year: 2013

Theoretical ab initio calculations are reported of the cross sections for dissociative recombination of the lowest four excited vibrational levels of N2(+) at electron energies from 0.001 to 1.0 eV. Rydberg vibrational levels contributing to the cross section structures are identified as are dissociative channels contributing more than 10(-16) cm(2) to the total cross sections. In contrast to the prior study of v = 0 (S. L. Guberman, J. Chem. Phys. 137, 074309 (2012)), which showed 2(3)u to be the dominant dissociative channel, 4(3)u is dominant for v = 1. Both 2 and 4(3)u are major routes for dissociative recombination from v = 2-4. Other routes including 2(3)u(+), 3(3)u, 2(1)u, 2(3)g, 2(1)g(+), 1(1)g, and b(1)u(+) are significant in narrow energy ranges. The results show that minor dissociative routes, included here for N2(+), must be included in theoretical studies of other molecular ions (including the simplest ions H2(+) and H3(+)) if cross section agreement is to be found with future high resolution dissociative recombination experiments. The calculated predissociation lifetimes of the Rydberg resonances are used in a detailed comparison to two prior storage ring experiments in order to determine if the prior assumption of isotropic atomic angular distributions at zero electron energy is justified. The prior experimental assumption of comparable cross sections for v = 0-3 is shown to be the case at zero but not at nonzero electron energies. Circumstances are identified in which indirect recombination may be visualized as a firefly effect.

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