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Flourescence properties of trendy molecules studied with synchrotron radiation
KTH, School of Engineering Sciences (SCI), Physics.
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis summarises the experimental results on molecular spectroscopy of gas phase molecules using synchrotron radiation in the UV- VUV and soft-X rays regions. The results of applying Photon Induced Fluorescence Spectroscopy (PIFS) to D2, H2S, H2O and pyrimidine are presented and discussed. Both inner and outer shell excitations of free molecules lead to different relaxation processes. However, a common result is that when the molecule breaks and the resulting neutral fragments are left in an excited state, they might fluoresce in the UV- Vis range. PIFS technique has two main advantages, it permits to detect neutral fragments and to identify the fluorescing species. From this fact, we can infer dissociation channels and trace back the electronic processes that led to the fluorescence. For these molecules we have analysed and interpreted both dispersed and undispersed fluorescence. What motivates our work is the lack of fluorescence studies and in a more general sense, to contribute to the knowledge of important molecules for life such as water and pyrimidine.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , ix, 47 p.
Series
Trita-FYS, ISSN 0280-316X ; 2006.57
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-4148ISBN: 91-7178-428-4 (print)OAI: oai:DiVA.org:kth-4148DiVA: diva2:10920
Presentation
2006-10-09, Sal FA31, AlbaNova universitetscentrum, Roslagstullsb 21, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101125Available from: 2006-10-13 Created: 2006-10-13 Last updated: 2010-11-25Bibliographically approved
List of papers
1. The npσ,π to EF emission systems in D2 studied by selective excitation
Open this publication in new window or tab >>The npσ,π to EF emission systems in D2 studied by selective excitation
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2005 (English)In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 38, no 6, 659-664 p.Article in journal (Refereed) Published
Abstract [en]

The np sigma 1 Sigma(u)(+) and np pi (1)Pi(u) states in D-2 have been selectively excited using monoenergetic synchrotron light in the range of 13.97-15.84 eV and the subsequent dispersed emission to the EF (1)Sigma(g)(+) state was observed using a grating spectrometer. In total, 18 emission bands from the levels n = 3-6 were studied and rotationally analysed. The intensities of the P and R branches relative to the Q branch were found to vary strongly in the np pi (1)Pi(u)(+)-EF(1)Sigma(g)(+) bands indicating the existence of predissociations of np pi (1)Pi(u)(+) levels above the dissociation limit D(1s) + D(2l).

Keyword
Absorption spectroscopy, Dispersion (waves), Dissociation, Electric excitation, Electron energy levels, Synchrotron radiation, Dispersed emissions, Emission bands, Grating spectrometers, Molecular hydrogen
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-7997 (URN)10.1088/0953-4075/38/6/004 (DOI)000228455000008 ()2-s2.0-16244367150 (Scopus ID)
Note
QC 20100916Available from: 2008-02-20 Created: 2008-02-20 Last updated: 2017-12-14Bibliographically approved
2. Fluorescence emission following core excitations in the water molecule
Open this publication in new window or tab >>Fluorescence emission following core excitations in the water molecule
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2006 (English)In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 39, no 5, 1101-1112 p.Article in journal (Refereed) Published
Abstract [en]

Photon-induced fluorescence spectroscopy has been used to study the fragmentation of the water molecule at the O 1s is edge. Fluorescence emission has been observed from the neutral fragments H, O and OH as well as from the ionic fragments O+ and OH+. The extracted fluorescence yields of the H Lyman-alpha emission and O 2p(3)(S-4)3p(P-3) -> 2p(3)(S-4)3s(S-3) transitions show the same structures as the total ion yield spectrum but with different relative intensities. The most intense fluorescence emission is restricted to the region of the core excitations, while above the O 1s ionization limit the signal is much weaker (in the case of H) or below the detection limit (O, OH and OH+). The fluorescence emission is concluded to follow from the following general cascade: the core-excited states decay by resonant Auger transitions, the final states reached undergo dissociation into ionic and neutral fragments, and fluorescence occurs from excited fragments. In the case of the OH (A(2)Sigma(+) -> X-2 Pi) emission, the decay of core-excited states through soft x-ray emission may also be responsible for the observed fluorescence.

Keyword
high-resolution photoabsorption, dispersed spectroscopy, h2o, dissociation, oh, d2o, photodissociation, photofragments, ultraviolet, radicals
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-5535 (URN)10.1088/0953-4075/39/5/009 (DOI)000237753700014 ()2-s2.0-33244473688 (Scopus ID)
Note
QC 20100910Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2017-11-21Bibliographically approved
3. Fluorescence emission from photo-fragments after resonant S 2p excitations in H2S
Open this publication in new window or tab >>Fluorescence emission from photo-fragments after resonant S 2p excitations in H2S
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2007 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 9, no 3, 389-395 p.Article in journal (Refereed) Published
Abstract [en]

Visible-UV fluorescence emission of gas-phase hydrogen sulfide, H2S, has been studied at the S 2p edge with synchrotron radiation excitation. Dispersed fluorescence measurements in the wavelength range 300 - 900 nm were taken at several photon energies corresponding to the excitations of the S 2p electrons to the unoccupied molecular and Rydberg orbitals. The spectra reveal fluorescence from the H, S, S+, HS and HS+ photo-fragments. H is found to be the strongest emitter at Rydberg excitations, while the emission from S+ is dominant at the molecular resonances and above the S 2p ionization thresholds. The intensities of hydrogen Lyman-alpha (122 nm), Balmer-alpha (656 nm), Balmer-beta (486 nm) transitions as well as the visible-UV total fluorescence yield (300 - 900 nm) and the total ion yield were measured by scanning the photon energy in small steps across the S 2p edge. The different Balmer lines show some sensitivity to the specific core excitations, which is, however, not so strong as that recently observed in the water molecule.

Keyword
X-RAY EXCITATION, DECAY CHANNELS, PHOTOELECTRON-SPECTROSCOPY, AUGER DECAY, MOLECULES, PHOTOIONIZATION, STATES, ATOMS
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-7998 (URN)10.1039/b610199b (DOI)000243204200008 ()2-s2.0-33845962796 (Scopus ID)
Note
QC 20100916Available from: 2008-02-20 Created: 2008-02-20 Last updated: 2017-12-14Bibliographically approved

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