1 / 27

Partial and differential electron impact ionization cross sections of acetylene

Partial and differential electron impact ionization cross sections of acetylene. S. Feil , K. G ł uch, S. Matt, P. Scheier and T. Märk Institut für Ionenphysik Universität Innsbruck A-6020 Innsbruck. LEIF – Meeting, Belfast 2003. Hochleistungswerkstoffe. About me:. Introduction.

millie
Download Presentation

Partial and differential electron impact ionization cross sections of acetylene

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Partial and differential electron impact ionization cross sections of acetylene S. Feil, K. Głuch, S. Matt, P. Scheier and T. Märk Institut für Ionenphysik Universität Innsbruck A-6020 Innsbruck LEIF – Meeting, Belfast 2003

  2. Hochleistungswerkstoffe • About me: Introduction Diploma thesis about: Physical and technological basics of Inductively coupled Vacuum Plasma Spraying (IVPS) At the Plansee Company in Reutte in Tirol

  3. Hochleistungswerkstoffe My job at Plansee Characterisation of the machine: Power measurements Temperatur measurements (in the spot) Particle velocity measurements Flame temperature measurements Development of new warmstrenthened materials Re10W (mixed crystal hardening) Re3Hf (reference) Re3HfN (dispersion hardening) Re3HfC (dispersion hardening)

  4. In April 2003 I started PhD. Mass spectrometry of molecules and clusters … on a double focussing mass spectrometer …our group Work partially supported by the FWF, ÖAW and ÖNB, Wien, Austria. We also thank the European Commission, Brussels.

  5. Why C2H2 ? Importance of electron collisional properties of acetylene for several reasons: edge plasmas in fusion reactors (wall-plasma-interaction) present in planetary and cometary atmospheres concentration of C2H2 in the atmosphere of earth is expected to nearly double by the year 2030 due to the increased use of automobiles C2H2 is a very simple molecule among hydrocarbons radiation chemistry ………

  6. What was done? Partial cross sections for electron impact ionization of C2H2 were measured from threshold to 900eV Ion kinetic energy distributions were deduced applying a deflection field method Determination of cross sections that are differential with respect to the initial energy of the ion Considering discrimination highly energetic fragment ions could be measured with a double focussing mass spectrometer in good agreement to specially dedicated instruments

  7. B-field E-field deflector plates detector z x y electron beam Discrepancies in the literature for cross sections of fragment ions • Specially dedicated instruments • Correction of data due to kinetic energy effectsa) integration of beam profile • b) determination of discrimination in the ion source Our apparatus Two sector field MS: NIER Type ion source

  8. Technique for Ekin determination Measurement: z – profile What is a z – profile? deflector plates electron beam

  9. Work schedule Measurement z - profile Experiment Smoothing (with gauss) then differentiate  distribution function Ekin = c×Uz2 Data analysis c from parent ions Include discrimination

  10. Example: CH+ out of C2H2 Ion beam profile: • splits the molecule • C2H2 + e  CH+ + CH + 2e • But: • C2H2 + e  C2H2++ + 3e • same m/q ratio

  11. Mass spectrum of C2H2 • More than 50% of m/q ratio 13 is C2H2++

  12. Example: CH+ out of C2H2 Measurement and gauss- smoothed curve Differentiated, squared and rescaled

  13. Example: CH+ out of C2H2 Corrected due to the discrimination Doing this analysis and finally integrate the kinetic energy distribution One can get partial cross sections of ions but with more information

  14. Final result: CH+ out of C2H2 Partial cross section CH+ & C2H2++ One can see the 3 different reaction channels dependent on the electron energy

  15. Identification of different channels Partial cross section CH+ & C2H2++ Appearance of this reaction channel at ~ 36eV Compare the red process with the ionization energy of C2H2++:

  16. Ionization Energy of C2H2++ One can deduce that the second (red) process comes purely from the doubly charged acetylene

  17. C2H2++ can`t be neglected ! Stability of this di-cation? check a decay reaction of C2H2++ (with MIKE technique)

  18. B-field E-field detector z x y electron beam Further investigations(C2H2++ C2H+ + H+) … with MIKE scan technique (m1 m2 + m3) Mass analysed Ion Kinetic Energy Selecting a mass Scanning the electric sector Identification:

  19. Further investigations(C2H2++ C2H+ + H+) The fragment C2H+ at Efrag* = 982.7V = 3.88eV The kinetic energy of C2H+ is then ~ 150meV.

  20. Conclusion it is possible to determine partial cross sections in good agreement with results obtained by using specially dedicated instruments The doubly charged fraction in the mass spectrum of C2H2 can`t be neglected With the present method it is possible to identify the different channels of the reaction processes The cross section of CH+ could be deduced by subtracting the „red process“ from the partial cross section

  21. Final result: H+ out of C2H2 One can see the 2 different reaction channels dependent on the electron energy

  22. H+ out of C2H2

  23. The NIER – Type source

  24. Example: CH+ out of C2H2 Measurement and gauss- smoothed curve Differentiated, squared and rescaled

  25. Example: CH+ out of C2H2 Corrected due to the discrimination function Doing this analysis with different electron energies and finally summing all graphs up One can get partial cross sections of ions but with more information

More Related