INTRODUCTION
1
INTRODUCTIO INTRODUCTIO N N WALL ASSOCIATION WALL ASSOCIATION DIAGNOSTICS DIAGNOSTICS RESULTS RESULTS CONCLUSIONS CONCLUSIONS ACKNOWLEDGEMENTS ACKNOWLEDGEMENTS Ro-vibrational excitation of hydrogen Ro-vibrational excitation of hydrogen formed by association in a very dense formed by association in a very dense expanding plasma expanding plasma Group Equilibrium and Transport in Plasmas Department of Applied Physics P.O. Box 513, 5600 MB Eindhoven The Netherlands P. Vankan , D.C. Schram, S.B.S. Heil, and R. Engeln FO M The authors greatly appreciate the skillful technical assistan of M.J.F. van de Sande, A.B.M. Hüsken, and H.M.M. de Jong. PLASMA PLASMA Probe ro-vibrational distribution in the electronic groundstate via X B transition widely tunable VUV photons necessary spectrally resolve transitions narrowband Method: Stimulated Anti-Stokes Raman Scattering (SARS) in H 2 , down tot 122 nm: •Large Raman shift of 4155.23 cm -1 •Hydrogen is transparant to generated VUV photons spatially resolved, high sensitivity required Laser Induced Fluorescence (LIF) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 2 4 6 8 10 12 14 16 18 VUV photon B u + X g + P otentialenergy (eV ) Inte rn u cle ar distan ce (Å) H 2 potential energy diagram EXPERIMENTAL SETUP EXPERIMENTAL SETUP PM T PM T H 2 LN 2 VUV m ono L W BS M M plasma W S W M M Nd:YAG THG Dye (C440) BBO M M 220 nm to pum p to pum p ! )! , ( 2 v r H H H adsorbed plasma also for O 2, N 2, NH 3, NO … The motivation is the study of the formation of molecules in flowing highly activated plasmas. If a dense plasma with atomic hydrogen radicals expands from a dense plasma source into a low pressure background H 2 (r,v) molecules are formed. The experiment focuses on the measurement of ro-vibrationally excited H 2 (r,v) molecules. These molecules are formed in association at surfaces under conditions of large radical fluxes. Strong non-thermal • H 2 (r,v) rotation/ vibration excitation • Low levels v=0, J=0-5 in thermal equilibrium • Additional population with high rotation/ vibration excitation • High r,v population in rough agreement with Goldberg-Waage dissociation-association balance • Mechanism: association at surface of H-atoms with H-atoms adsorbed at surface. • Plasma dissociates - surface associates • Significant chemical potential! H 2 (r,v) + e H - + H ,H 2 (r,v) + mol mol 1 + H [email protected] 20 Hz rep.rate SHG of dye laser: 5-10 mJ @ 230 nm Vacuum system due to O 2 absorption < 195 nm optical path under vacuum. p~10 -5 mbar Plasma cascaded arc source (I=60 A, V=140V) expanding H 2 plasma ( 3 slm) background pressure 10-100 Pa III III II I Association at surfaces H source recirculation VUV-LIF setup is used to study the H 2 (r,v) density 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 10 8 10 10 10 12 10 14 10 16 10 18 10 20 10 22 10 8 10 10 10 12 10 14 10 16 10 18 10 20 10 22 B oltzm ann Guldberg-Waage v=6 v=4 v=2 v=1 v=0 n /g H (m -3 ) n /g H r,v 2 (m -3 ) E n e rg y (e V ) VU V-LIF CARS Density of H 2 (r,v) per statistical weight H 2 H 2 43650 43700 43750 43800 43850 43900 0 2 4 6 8 10 2 ,12 6,1 6,1 3,7 1,15 1 ,12 1 ,11 3,5 3,6 2 ,4 /2 ,1 2 0 ,19 F lu o re sce n ce (a .u .) S H fre q u e n cy (cm -1 ) rt of the VUV-LIF spectrum of H 2 (r,v)
description
(Å). H 2. H 2. 1 2. Group Equilibrium and Transport in Plasmas Department of Applied Physics P.O. Box 513, 5600 MB Eindhoven The Netherlands. Ro-vibrational excitation of hydrogen formed by association in a very dense expanding plasma. P. Vankan , D.C. Schram, S.B.S. Heil, and R. Engeln. - PowerPoint PPT Presentation
Transcript of INTRODUCTION
INTRODUCTIINTRODUCTIONON
WALL WALL ASSOCIATIONASSOCIATION
DIAGNOSTICSDIAGNOSTICS
RESULTSRESULTS
CONCLUSIOCONCLUSIONSNS
ACKNOWLEDGEMENTSACKNOWLEDGEMENTS
Ro-vibrational excitation of hydrogen Ro-vibrational excitation of hydrogen formed by association in a very dense formed by association in a very dense
expanding plasmaexpanding plasma
Group Equilibrium and Transport in Plasmas
Department of Applied PhysicsP.O. Box 513, 5600 MB Eindhoven
The Netherlands
P. Vankan, D.C. Schram, S.B.S. Heil, and R. Engeln
FOM
The authors greatly appreciate the skillful technical assistance
of M.J.F. van de Sande, A.B.M. Hüsken, and H.M.M. de Jong.
PLASMAPLASMA
Probe ro-vibrational distribution inthe electronic groundstate via X B transitionwidely tunable VUV photons necessary
spectrally resolve transitions
narrowband
Method: Stimulated Anti-Stokes Raman Scattering (SARS) in H2, down tot 122 nm: •Large Raman shift of 4155.23 cm-1
•Hydrogen is transparant to generated VUV photons spatially resolved, high sensitivity required
Laser Induced Fluorescence (LIF)
0.0 0.5 1.0 1.5 2.0 2.5 3.00
2
4
6
8
10
12
14
16
18
VUV photon
B u
+
X g
+
Po
ten
tial e
ne
rgy
(eV
)
Internuclear distance (Å)
H2 potential energy diagram
EXPERIMENTAL EXPERIMENTAL SETUPSETUP
PMT
PMT
H2
LN2
VUV mono
L W
BS
MM
plasma
W
S
WM
M
Nd:YAGTHG
Dye (C440)
BBO
M
M
220 nm
to pump
to pump
!)!,(2 vrHHH adsorbedplasma also for O2, N2, NH3, NO …
The motivation is the study of the formation of molecules in flowing highly activated plasmas. If a dense plasma with atomic hydrogen radicals expands from a dense plasma source into a low
pressure background H2 (r,v) molecules are
formed. The experiment focuses on the
measurement of ro-vibrationally excited H2(r,v)
molecules. These molecules are formed in association at surfaces under conditions of large radical fluxes.
Strong non-thermal
• H2(r,v) rotation/ vibration excitation
• Low levels v=0, J=0-5 in thermal equilibrium• Additional population with high rotation/ vibration excitation• High r,v population in rough agreement with Goldberg-Waage dissociation-association balance• Mechanism: association at surface of H-atoms with H-atoms adsorbed at surface.• Plasma dissociates - surface associates• Significant chemical potential!
H2 (r,v) + e H- + H ,H2 (r,v) + mol mol1 + H
20 Hz rep.rateSHG of dye laser: 5-10 mJ @ 230 nm
Vacuum systemdue to O2 absorption < 195 nm optical path under vacuum.
p~10-5 mbar
Plasmacascaded arc source (I=60 A, V=140V)expanding H2 plasma ( 3 slm)background pressure 10-100 Pa
III
III
II
I
Association at surfaces
H source
recirculation
A VUV-LIF setup is used to study the H2(r,v) density
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5108
1010
1012
1014
1016
1018
1020
1022
108
1010
1012
1014
1016
1018
1020
1022
Boltzmann
Guldberg-Waage
v=6
v=4
v=2v=1
v=0
n/g
H (
m-3)
n/g
H r
,v
2 (
m-3)
Energy (eV)
VUV-LIF CARS
Density of H2(r,v) per statistical weight
H2
H2
43650 43700 43750 43800 43850 43900
0
2
4
6
8
10
2,12
6,1
6,1
3,7
1,15
1,12
1,11
3,5
3,6
2,4
/ 2,1
2
0,19
Flu
ores
cenc
e (a
.u.)
SH frequency (cm-1)
Part of the VUV-LIF spectrum of H2(r,v)
