Partial cross sections for dissociative electron attachment to tetrahydrofuran reveal a dynamics-driven rich fragmentation pattern

We report partial absolute cross sections for dissociative electron attachment (DEA) to tetrahydrofuran C₄H₈O. The high sensitivity of the present setup, quantitative DEA spectrometer with time-of-flight analyzer, led to identification of a number of previously unreported fragments (CH₂⁻, OH⁻, CHO⁻, C₄H₅O⁻, C₃H₃⁻) thus revealing complex dissociation dynamics of the involved resonant states. The chemical composition of fragment anions was assigned by experiments with completely deuterated tetrahydrofuran. We also show that the dominant heavy anionic fragment with m/z = 41 is C₃H₅⁻ anion rather than C₂HO⁻ as reported in the previous studies, in spite of the fact that formation of the latter one is energetically more favorable. The dynamics on the resonant state is thus more decisive for the reaction outcome than the asymptotic energetics. The assignment of resonances and their dynamic pathways is discussed by using comparison with recent complementary experiments that characterize electronic states of neutral and ionic tetrahydrofuran

Roadmap on dynamics of molecules and clusters in the gas phase

status: publishe

Absolute cross sections for elastic electron scattering from methylformamide

Elastic electron scattering from gaseous methylformamide (N-methylformamide, C 2H 5NO) has been investigated. Absolute elastic differential cross sections (DCSs) were determined both experimentally and theoretically for the incident energies from 50 to 300 eV. The measurements were performed using a cross-beam technique, for scattering angles from 20° to 110°. Relative elastic DCSs were measured as a function of both the angle and the incident energy and the absolute DCSs were determined using the relative flow method. The calculations of electron interaction cross sections are based on a corrected form of the independent-atom method, known as the SCAR (screen corrected additivity rule) procedure and using an improved quasifree absorption model. Calculated integral cross sections have been presented, as well, both for methylformamide and formamide, in the energy range 10-1000 eV, and discussed. The results are compared with and discussed regarding existing data for other small molecules representing building blocks of large biomolecules. © 2012 American Physical Society.The work was supported by the Ministry of Education and Science of Republic of Serbia (Project No. 171020) and Spanish Ministerio de Ciencia e Innovacion Project No FIS2009-10245, and motivated by the COST Action MP1002 (Nano-IBCT).Peer Reviewe

Design and performance of an instrument for electron impact tandem mass spectrometry and action spectroscopy of mass/charge selected macromolecular ions stored in RF ion trap*

A new apparatus was designed, coupling an electron gun with a linear quadrupole ion trap mass spectrometer, to perform m/z (mass over charge) selected ion activation by electron impact for tandem mass spectrometry and action spectroscopy. We present in detail electron tracing simulations of a 300 eV electron beam inside the ion trap, design of the mechanical parts, electron optics and electronic circuits used in the experiment. We also report examples of electron impact activation tandem mass spectra for Ubiquitin protein, Substance P and Melittin peptides, at incident electron energies in the range from 280 eV to 300 eV

Absolute cross sections for electron scattering from furan

We report results of measurements and calculations of absolute cross sections for electron scattering from furan molecules (C 4H 4O). The experimental absolute differential cross sections (DCSs) for elastic electron scattering were obtained for the incident energies from 50 eV to 300 eV and for scattering angles from 20 to 110, by using a crossed electron-target beam setup and the relative flow technique for calibration to the absolute scale. The calculations of the electron interaction cross sections are based on a corrected form of the independent-atom method, known as the screening corrected additivity rule (SCAR) procedure and using an improved quasifree absorption model. The latter calculations also account for rotational excitations in the approximation of a free electric dipole and were used to obtain elastic DCSs as well as total and integral elastic cross sections which are tabulated in the energy range from 10 to 10 000 eV. All SCAR calculated cross sections agree very well with both the present and previously published experimental results. Additionally, calculations based on the first Born approximation were performed to calculate both elastic and vibrationally inelastic DCSs for all the modes of furane, in the energy range from 50 eV to 300 eV. The ratios of the summed vibrational to elastic DCSs are presented and discussed. Finally, the present results for furan are compared with previously published elastic DCSs for the tetrahydrofuran molecule and discussed. © 2012 American Institute of Physics.American Institute of Physics#Supported by the Ministry of Education and Science of Republic of Serbia (Project No. 171020) and Spanish Ministerio de Ciencia e Innovación Project No. FIS2009-10245, and motivated by the COST Action MP1002 (Nano-IBCT). R.C. acknowledges support of the Czech Ministry of Education (Grant No. OC10046) and the Grant Agency of the Czech Republic (Grant No. P208/11/0452).Peer Reviewe

Absolute differential cross sections for elastic scattering of electrons from pyrimidine

7 pags. ; 3 figs. ; 1 tab.Differential cross sections DCSs for elastic scattering of electrons from pyrimidine C4 H4 N2 are presented for incident energies from 50 to 300 eV. The measurements were performed using a cross beam technique, for scattering angles from 20° to 110°. The relative DCSs were measured as a function of both the angle and incident energy and the absolute DCSs were determined using the relative flow method. The calculations of electron interaction cross sections are based on a corrected form of the independent-atom method, known as the screen corrected additivity rule procedure and using an improved quasifree absorption model. Calculated results agree very well with the experiment. ©2009 The American Physical SocietyThis work was supported through Project No. 141011 fi- nanced by the Ministry of Science and Technological Development of Republic of Serbia and the Spanish Ministerio de Ciencia e Innovacion Project No. FISI2006-00702 . The present work was also motivated by research within COST Actions P9 “Radiation Damage in Biomolecular Systems” and CM0601 “Electron Controlled Chemical Lithography ECCL .”Peer reviewe