PowerPointPrsentation

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.
t0
tc
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, v0 and v1, 337 and
316nm t0 41.7ns (for both v) kq 1.210-11
cm3/s and kq 2.510-11 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, v0, 1
Non radiative quenching Collisional quenching of
v levels by N2 Radiative transition
B, v0, 1, etc.
A model worked out by Andrei Morozov showed an
increase of the p value for the 337nm (v0 to
v0) 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
n1
Q1p
v0
t0 Q1p t1 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