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Lyman and Balmer emission following core excitations in methane and ammonia molecules
KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
CNR-INFM, Laboratorio Nazionale TASC.
CNR-INFM, Laboratorio Nazionale TASC.
Show others and affiliations
2007 (English)In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 40, no 8, 1489-1500 p.Article in journal (Refereed) Published
Abstract [en]

The intensities of hydrogen Lyman-alpha and Balmer series emission lines as a result of photoexcitation of free CH4 and NH3 molecules at the C 1s and N 1s edges have been measured. For methane, the total fluorescence yield in the visible region ( 300 - 650 nm) was also recorded. Excitation functions of the Balmer lines show relative intensity enhancement of Balmer-beta emission in comparison with Balmer-alpha at higher core- to- Rydberg excitations. The Lyman-alpha emission intensity, in general, follows the relations observed in the corresponding total ion yield measurements. Additionally, the Balmer-gamma and -delta yields were measured for ammonia molecules and they show intensity maxima at photon energies shifted closer to the N 1s threshold than Balmer-alpha and -beta. A quantum defect analysis is performed to find out which core excitations are responsible for this enhanced intensity. Dissociation pathways leading to the emission in H atoms are discussed.

Place, publisher, year, edition, pages
2007. Vol. 40, no 8, 1489-1500 p.
Keyword [en]
Ammonia, Dissociation, Fluorescence, Methane, Photons, Rydberg states, Balmer series emission lines, Core excitations, Photon energies, Quantum defect analysis, Rydberg excitations
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-7999DOI: 10.1088/0953-4075/40/8/003ISI: 000246010300004Scopus ID: 2-s2.0-34247098021OAI: oai:DiVA.org:kth-7999DiVA: diva2:13201
Note
QC 20100916Available from: 2008-02-20 Created: 2008-02-20 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Synchrotron radiation studies of gas phase molecules: from hydrogen to DNA sugars
Open this publication in new window or tab >>Synchrotron radiation studies of gas phase molecules: from hydrogen to DNA sugars
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis summarises experimental results on the molecular spectroscopy of gas phase molecules excited by synchrotron radiation in the VUV and soft X-ray regions. We have used three different detection techniques, photon induced fluorescence spectroscopy, photoionisation mass spectroscopy and near edge X-ray absorption fine structure spectroscopy to study molecular deuterium, hydrogen sulphide, ammonia, methanol, pyridine, pyridazine, pyrimidine, pyrazine, s-triazine, and 2-deoxy-D-ribose, the last one also known as the DNA sugar. Out of this variety of techniques and molecules we have shown that: (1) high resolution dispersed fluorescence allows us to identify vibrational and rotational bands in molecular deuterium, as well as to estimate the predissociation probability of the same molecule [paper I]; (2) the main species fluorescing after core excitation of methane, ammonia [paper III], hydrogen sulphide [paper II], pyridine, pyrimidine and s-triazine is H Balmer α, followed by fluorescence from ionised species, molecular bands and Balmer β, γ , δ; (3) the Rydberg enhancement seen in fluorescence measurements of water [Melero et al. PRL 96 (2006) 063003], corroborated later in H2S [paper II], NH3 [paper III] and CH4 [paper III] and postulated as general behaviour for molecules formed by low-Z atoms, is also seen in larger organic cyclic molecules, e.g. azabenzenes; (4) when dissociative ionisation of pyridine, pyridazine, pyrimidine, pyrazine, s-triazine and 2-deoxy-D-ribose occurs, concerted bond rearrangement and nuclear motion takes place as opposed to stepwise dissociation [papers V and VI].

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. x, 56 p.
Series
Trita-FYS, ISSN 0280-316X ; 2008:1
Keyword
KTH thesis, synchrotron radiation, gas phase, bio molecules
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-4640 (URN)978-91-7178-852-8 (ISBN)
Public defence
2008-03-13, FA31, Albanova, Roslagstullabacken 21, Stockholm, 10:15
Opponent
Supervisors
Note
QC 20100916Available from: 2008-02-20 Created: 2008-02-20 Last updated: 2010-09-16Bibliographically approved
2. Development of visible spectroscopic techniques for applications in plasma diagnostics
Open this publication in new window or tab >>Development of visible spectroscopic techniques for applications in plasma diagnostics
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

In this thesis visible spectroscopy is developed and used for two applications.

Studies of motional Stark effect spectra for diagnosing the current distribution in the fusion plasmas with two different spectroscopic diagnostic systems: ratiometry and interferometry. Both systems provide non-invasive method for diagnosis of the internal plasma properties, e.g. magnetic field. Pitch angle of magnetic field lines are obtained from polarisation of Stark split Hα spectral lines emitted by energetic hydrogen atoms injected into the plasma volume by neutral beam. Several methods of calibration of the systems on TEXTOR and JET are discussed. The main result of this work is the first measurement of the safety factor radial profile with new ratiometric MSE system on TEXTOR.

Studies of molecular fragmentation of free molecules CH4 and NH3 excited with synchrotron radiation by detection of the fluorescence from the fragments. The results give the decay path ways for the molecules when excited below the N and C ionisation edges.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. xi, 39 p.
Series
Trita-FYS, ISSN 0280-316X ; 2006:66
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-4252 (URN)91-7178-479-9 (ISBN)
Presentation
2006-12-12, FA31, AlbaNova univ. centrum, Roslagstullsgatan 21, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101116Available from: 2006-12-22 Created: 2006-12-22 Last updated: 2010-11-17Bibliographically approved

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Rachlew, Elisabeth

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