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Laboratory Experiments for Studying the Emission of Nitrogen and Air

Laboratory Experiments for Studying the Emission of Nitrogen and Air Andreas Ulrich, Andrei Morozov Technische Universität München Fakultät für Physik E12 4th Air Fluorescence Workshop May 17-20, 2006, Prague - Pruhonice. Excitation of dense gases with low energy electron beams

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Laboratory Experiments for Studying the Emission of Nitrogen and Air

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  1. Laboratory Experiments for Studying the Emission of Nitrogen and Air Andreas Ulrich, Andrei Morozov Technische Universität München Fakultät für Physik E12 4th Air Fluorescence Workshop May 17-20, 2006, Prague - Pruhonice

  2. Excitation of dense gases with low energy electron beams • Shape of the excited volume • Correlation of quenching rate constants k and p‘ values • Intensity ratios of N2 emission bands (experiments in Chicago and Garching) • Improvements

  3. I) Excitation of dense gases with low energy electron beams Typical parameters: Electron energy: 15 keV Beam current: 10 μA average Pulses: 5 ns minimum Gas pressure: 0.1 – 2 bar Membrane: 300 nm SiNx

  4. Experimental setup

  5. Motivation for using low energy electrons for N2 emission studies: High fluorescence yield at low energy Copied from DPG-presentation 2006: Andreas Obermeier

  6. II) Shape of the excited volume The shape can be modelled using the program: „casino“ (P. Drouin, A. R. Couture, R. Gauvin, P. Hovington, P. Horny, H. Demers, Univ. de Sherbrooke, Quebec, Canada (2002)) This will be important for absolute emission measurements using low energy electron beams!

  7. III) Correlation of quenching rate constants k and p‘ values Rprod. τ0 τc

  8. The two approaches: time spectra pressure dependence Nagano et al. astro-ph/0303193 v3 26 Aug. 2003 the connection

  9. Example: N2 2P-Band, v=0 and v=1, 337 and 316nm τ0 = 41.7ns (for both v) kq = 1.2×10-11 cm3/s and kq = 2.5×10-11 cm3/s, respectively Results in p‘ = 74.6 hPa and p‘ = 35.8 hPa, respectively (10% error) Morozov et al. Eur. Phys. J. D 33, 207 (2005) In contrast to: p‘ = 151.7 hPa and p‘ = 88.3 hPa, respectively (10% error) Nagano et al. astro-ph/0303193 v3 26 Aug. 2003 ?

  10. Potential reasons for the discrepancy: Systematic errors ? Collisional mixing of the vibrational levels ? See: J. M. Calo and R. C. Axtmann, J. Chem. Phys. 54, 1332 (1971) C, v=0, 1 Non radiative quenching Collisional quenching of v – levels by N2 Radiative transition B, v=0, 1, etc. A model worked out by Andrei Morozov showed an increase of the p‘ value for the 337nm (v‘=0 to v=0) transition from 79.36 to 91.95 hPa using the data given in the publication by Calo and Axtmann. (I(p) modelled with and without coll. quenching of v levels and then fit using the regular formular.)

  11. n=1 Q1p v=0 τ0 Q1p τ1 Q1dp

  12. First test of the influence of vibrational relaxation via collisions: Classical model, new model with vibrational relaxation, data from new model fit with classical model

  13. Intensity ratios of nitrogen emission bands Spectral response of McPherson 218. Preliminary measurements: Black: W Strip-lamp Blue: W Strip- lamp + UG11 Red: D2 Lamp

  14. Spectral response of the „Rome“ spectrometer Measured with a calib. halogen and a Hg pen-ray lamp, respectively

  15. Spectrum of air recorded using electron beam excitation, McPherson model 218 VUV monochromator and photon counting:

  16. Comparison of spectra of laboratory air excited by 10 keV photons (photoelectrons) and 10 keV electrons (APS Chicago and e- beam Graching)

  17. Comparison of spectra of laboratory air excited by 10 keV photons (photoelectrons) and 10 keV electrons (APS Chicago and e- beam Graching) Detail:

  18. Comparison of the weakest and strongest lines analysed (Garching data):

  19. Relative intensities of N2 emission bands: Comparison of Chicago and Garching data with literature values

  20. Relative intensities of N2 emission bands: Comparison of Chicago and Garching data with literature values Log – scale:

  21. Analysis of the same Garching- data, two persons independently

  22. Improvements: We have bought a 100 W calibrated halogen lamp (LOT / Heraeus) We will borrow a new calibrated D2 from GSI-Darmstadt (Plasma physics group) Measurements of the absolute photon flux will be performed Pressure dependences should be measured for the ~10 keV electrons Acknowledgement ! Many thanks to Paolo Privitera, Hans Klages and all their coworkers for inviting me to participate in the Chicago experiment and KfA-Karlsruhe for paying for the trip. Thanks to Reiner Krücken and MLL for supporting my trip to this conference. I want to thank Jochen Wieser (TuiLaser/Coherent) for his help with the experiments and the apparatus, in particular the very stable power supply. Thank you for your attention

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