gas phase spectroscopy at the cls
DESCRIPTION
VLS-PGM BeamlineTRANSCRIPT
![Page 1: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/1.jpg)
Gas phase spectroscopy at the CLS
http://www.lightsource.ca
![Page 2: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/2.jpg)
VLS-PGM Beamline
Y Hu et al, Rev. Sci. Instrum. 78 (2007) p083109
![Page 3: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/3.jpg)
VLS-PGM Beamline
![Page 4: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/4.jpg)
VLS-PGM Beamline
![Page 5: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/5.jpg)
Instruments for gas-phase science at the VLS-PGM beamline
Dual toroidal electrostatic analyser
Wiley-McLarentime-of-flightmass spectrometer
![Page 6: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/6.jpg)
Dual toroidal analyser
T J Reddish et al (1997) Rev. Sci. Instrum. 68 2685A E Slattery et al (2000) J. Phys. B. 33 4383
• Toroidal analysers can energy select the charged particles (ions/ electrons) while preserving the initial angle of emission.
• Both analysers are independent and each can be switched to detect electrons or ions.
• Both can operate in threshold (TPES) mode• Detectors can operate in coincidence mode
![Page 7: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/7.jpg)
9 10 11 12 13 14 15 16 170
5000
10000
15000C
ount
s
Binding Energy / eV
Pyridine h = 80eV
Dual toroidal analyser
![Page 8: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/8.jpg)
Dual toroidal analyser
10 12 14 160.0
0.1
0.2
0.3
0.4S
igna
l
Photon Energy / eV
Pyridine TPES
![Page 9: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/9.jpg)
Dual toroidal analyser
12.0 12.2 12.4 12.6 12.8 13.00.0
0.1
0.2
0.3
0.4
Sig
nal
Photon Energy / eV
Pyridine TPES
9.0 9.2 9.4 9.6 9.8 10.00.0
0.1
0.2
0.3
0.4
Sig
nal
Photon Energy / eV
Pyridine TPES
![Page 10: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/10.jpg)
Dual toroidal analyser
1cos3
21
4cos1
42
2
P
dd
Since the toroidal analyser preserves the azimuthal angle of emission of the photoelectron we can find the photoelectron asymmetry parameter across a photoelectron spectrum.
That is we can record “beta paramer” spectra.
The spectra here are beta parameter spectra for H2 and will be the subject of the 2nd half of this talk.
Finally we remember that the detectors can be configured for electrons or ions.
![Page 11: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/11.jpg)
Time of Flight
Electron Start – Ion Stop, with multi-hit electronicsNo energy discrimination on the electron
Allows ToF mass spectra and PePIPICO 2D maps
![Page 12: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/12.jpg)
Time of Flight
0 20 40 60 800
1000
2000
3000
4000
5000C
ount
s
Mass / amu
Pyridazine h=170eV
Parent
“C4”
“C3”
“C2”Water
“C1”
![Page 13: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/13.jpg)
ToF PePIPICO
10000 20000 30000 40000 50000
10000
20000
30000
40000
50000ToF Ion #2
3.621E4
2.559E4
3.935E4
N02 + C3 fragments
C3 + C4 fragments
C + O
(H)CN + NH
(H)CN + C3
(H)CN +C5H5
Mass 29 ?
2 Fragment dissociation = 45
Otherwise could be any angle
0 50100150200250
-NO2
-NO
C5H5
C5H6N
0
50
100
NONO2
ToF
Ion
#1
para-nitroaniline
![Page 14: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/14.jpg)
Time of Flight
![Page 15: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/15.jpg)
http://www.lightsource.ca
If any of this would be of interest to you please talk to me at this symposium.
Michael MacDonaldCanadian Light Source Inc.44 Innovation BoulevardSaskatoon, SK, S7N 2V3306 657 3812
![Page 16: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/16.jpg)
Hydrogen
![Page 17: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/17.jpg)
Hydrogen
![Page 18: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/18.jpg)
HydrogenDirect mechanisms (a) and (b) produce only a limited range of electron energies due to Franck-Condon Factor restrictions
Indirect mechanisms (c) and (d) produce a wide range of electron kinetic energies.
Further mechanism (d) can decay to either the bound σg or dissociative σu state of the ion.
Remember in quantum mechanics indistinguishable paths to the same destination interfere.
![Page 19: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/19.jpg)
Hydrogen
![Page 20: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/20.jpg)
Red – experimental results
Black – full QM closed coupling calculations
![Page 21: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/21.jpg)
Hydrogen
![Page 22: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/22.jpg)
Hydrogen
![Page 23: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/23.jpg)
![Page 24: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/24.jpg)
Results and the simplified model
![Page 25: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/25.jpg)
Summary of H2 results
Unusual properties of observed interference• Interference shows in direction of photoelectrons not
intensity• Direction of photoelectrons are dictated by nuclear
motion (Ultimately it all comes back to symmetry !) • Interference is from different autoionisation paths from a
coherent superposition of electronic states. (Not direct ionisation and autoionisation from a single excited state)
• This is not a coincidence experiment, and, indeed, the oscillations would disappear in a coincidence experiment.
![Page 26: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/26.jpg)
![Page 27: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/27.jpg)
AcknowledgementsDr. Tim ReddishDr. Arathi Padmanabhan
Dr. Smialek-Telega
Prof. Nigel Mason
Dr. Lucia ZuinRu Igarishi
Antonio C.O. Guerra and Cássia C. Turci Instituto de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-909, Brazil
Dr. J. FernándezDr. A. Palacios Prof. F. Martín
![Page 28: Gas phase spectroscopy at the CLS](https://reader036.vdocuments.us/reader036/viewer/2022062401/5a4d1b107f8b9ab05998eb4a/html5/thumbnails/28.jpg)