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Experimental station for gas phase fluorescence spectroscopy
KTH, Superseded Departments, Physics.
KTH, Superseded Departments, Physics.
KTH, Superseded Departments, Physics.
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2004 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 75, no 7, 2402-2408 p.Article in journal (Refereed) Published
Abstract [en]

The details of an experimental setup for gas phase atomic and molecular fluorescence measurements using synchrotron radiation are described in this article. The most significant part of the apparatus is an optical arrangement, which allows for simultaneous measurements of dispersed as well as total fluorescence intensity using an effusive gas jet and an inbuilt gas cell assembled in a convenient plug and measure configuration. The first measurements concerning fluorescence of the N-2 molecule around the N 1s edge obtained with this setup are presented.

Place, publisher, year, edition, pages
2004. Vol. 75, no 7, 2402-2408 p.
Keyword [en]
dispersed fluorescence, n2 molecule, photoionization, n-2, excitation, resonances, states
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-6869DOI: 10.1063/1.1764605ISI: 000222847900027Scopus ID: 2-s2.0-3843064413OAI: oai:DiVA.org:kth-6869DiVA: diva2:11700
Note
QC 20100910Available from: 2004-11-30 Created: 2004-11-30 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Synchrotron radiation induced fluorescence spectroscopy of gas phase molecules
Open this publication in new window or tab >>Synchrotron radiation induced fluorescence spectroscopy of gas phase molecules
2004 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

A new experimental set-up for gas phase fluorescence studies using synchrotron radiation has been designed and constructed to perform simultaneously total and dispersed fluorescence measurements.

Neutral photodissociation of CO has been investigated after excitation with 19-26 eV photons. Fluorescence from 3p 3P, 3p 3S and 3p 1D excited states in carbon was recorded and interpreted by ab initio calculations. The population and dissociation of states belonging to the C and D Rydberg series in CO seem to explain the production of the observed triplet states but not the 3p 1D state.

Neutral photodissociation of NO is reported in the 17-26 eV energy range. No known molecular states can account for the collected data. New information regarding the precursor states of the observed neutral dissociation is provided by ab initio calculations.

Autoionization of superexcited states in molecular nitrogen is evidenced by strong deviations of the Franck-Condon ratio in the fluorescence of the N2+ B state. Ab initio calculations predict the existence of autoionizing-excited states that may account for some of the observed structures in the 20-46 eV energy range.

Selective molecular fluorescence from the npó1Óu+ and npð 1Ðu (n=3-7) Rydberg levels to the E,F 1Óg+ state in H2 was recorded and rotationally analyzed. Vibrational levels of the E,F 1Óg+ state (vEF =0,1,3,6-10) are determined. The predissociation of npð 1Ð+ levels is observed in agreement with the literature.

Fragmentation of SF6 was investigated after excitation with 25–80 eV photons. Dispersed fluorescence measurements reveal the emission of S, S+, F and F+ excited atoms. These fragments are produced after single, double and triple excitations as well as direct ionizations and shake-ups in SF6.

Photoabsorption and fluorescence yield have been measured in SF5CF3 using 10-30eV photons. The photoabsorption spectrum can be explained in terms of its similarities to those of the SF6 and CF4 molecules. The dispersed and un-dispersed fluorescence resemble those of the CF3X family. Several features suggest the migration of an F atom across the S-C bond that fragments the molecule producing excited CF4.

Doubly excited states of H2 have been investigated in the range of 26-60 eV by monitoring Balmer á emission. The experimental data show the already known emission correlated with the fragmentation of the Q1 and Q2 states, and new features which could be attributed to dissociative photoionization and higher lying doubly excited states Qn (n>2) of the hydrogen molecule

Place, publisher, year, edition, pages
Stockholm: Fysik, 2004
Series
Trita-FYS, ISSN 0280-316X ; 2004:63
Keyword
Physics, molecular spectroscopy, photon induced fluorescence, synchrotron radiation, superexcited states, Fysik
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-43 (URN)91-7283-877-9 (ISBN)
Public defence
2004-11-12, FB53, AlbaNova, Stockholm, 10:00
Opponent
Supervisors
Available from: 2004-11-30 Created: 2004-11-30 Last updated: 2012-03-20
2. Synchrotron radiation spectroscopy of molecular dynamics beyond the valence shell
Open this publication in new window or tab >>Synchrotron radiation spectroscopy of molecular dynamics beyond the valence shell
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis presents experimental results on molecular spectroscopy of gas phase molecules using synchrotron radiation. It deals mainly with dynamical processes following resonant excitation of electrons from core and inner-valence shells of the following systems H2O, H2, SF6 and CD4. In order to reach these deep electrons and excite them photons in the energy range from 25 to 550 eV were used, depending on the particular system.

Two experimental techniques are used. Photon induced fluorescence spectroscopy is used to study the fluorescence emission of fragments after the decay of resonant coreexcited states for the water molecule, and after doubly excited states and resonant excitations of inner-shell electrons for H2 and SF6 respectively. Only the emission in the visible and near infrared range (300-900nm) and the Lyman-α transitions are measured. Energy resolved electron-ion coincidence is used for the study of the fragmentation of CD4 and SF6 after selective ionisation of one of the outer-valence orbitals. In the case of CD4 the fragmentation is compared for the cases in which the ionisation is done directly, or through participator Auger decay of different resonantly core-excited states.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. xiv, 59 p.
Series
Trita-FYS, ISSN 0280-316X ; 2006:13
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-3899 (URN)91-7178-294-X (ISBN)
Public defence
2006-04-20, Sal FB 53, AlbaNova, Roslagstullsbacken 21, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100910Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2010-09-10Bibliographically approved

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