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Stark Spectroscopy, Lifetimes and Coherence Effects in Diatomic Molecular Systems
Stockholm University, Faculty of Science, Department of Physics.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this dissertation is exemplified how different laser based methods are applied in high-resolution spectroscopic studies of internal properties of diatomic molecules.

A molecular beam apparatus assembly is described, where a laser ablation source is combined with a time-of-flight mass spectrometer. Compounds investigated with this equipment are hafnium sulfide and hafnium oxide. The molecules are excited and ionized applying the resonant two-photon ionization (R2PI) scheme, which is a sensitive absorption and detection technique for probing the population of an excited state.

By means of the DC Stark effect, permanent electric dipole moments of HfS in the D 1Π state and HfO in the b 3Π1 state are determined while the molecules are exposed to a static electric field. Under field-free conditions low temperature rotationally resolved spectra are recorded, generating line positions from which molecular parameters are derived.

The R2PI method, modified with an adjustable delay time, is also used in lifetime measurements of individual rotational levels of the HfS D 1Π and HfO b 3Π1 states. Oscillator strengths for transitions from the ground state are calculated, and in this connection basic concepts like Einstein coefficients, line strengths and Hönl-London factors, are surveyed. Theoretical calculation of lifetimes is discussed in view of the fact that a commonly available computer program (LEVEL 7.5 by Le Roy) gives erroneous output.

Some coherence and quantum interference related phenomena, such as electromagnetically induced transparency (EIT) and Autler-Townes (AT) splitting, are presented in the latter part of this thesis. Fundamental concepts and relations are introduced and explained. The driven three-level cascade system is elucidated, including some of its experimental applications to alkali metal dimers, Na2 and Li2.

A triple resonance spectroscopy experiment is described in terms of a three-laser, four-level inverted-Y excitation scheme, implemented in Na2. The accompanying density matrix formalism, providing the basis for theoretical simulations, is accounted for. From analysis of the results an absolute value of the electric dipole moment matrix element (transition moment) is extracted, using the AC Stark effect.

Some recently reported unexpected experimental results and unforeseen features, occurring in Doppler broadened samples and related to the open character of molecular systems, are briefly commented.

Place, publisher, year, edition, pages
Stockholm: Fysikum , 2005. , 86 p.
Keyword [en]
diatomic, dipole moment, Stark effect, lifetimes, transition moment, coherence effects, EIT, Autler-Townes
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:su:diva-650ISBN: 91-7155-125-5 (print)OAI: oai:DiVA.org:su-650DiVA: diva2:196576
Public defence
2005-10-07, sal FD5, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00
Opponent
Supervisors
Available from: 2005-09-12 Created: 2005-09-12Bibliographically approved
List of papers
1. On the dipole moments of some excited electronic states of HfS and HfO
Open this publication in new window or tab >>On the dipole moments of some excited electronic states of HfS and HfO
2004 In: Journal of Molecular Spectroscopy, ISSN 0022-2852, Vol. 224, no 2, 157-163 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-24044 (URN)
Note
Part of urn:nbn:se:su:diva-650Available from: 2005-09-12 Created: 2005-09-12Bibliographically approved
2. Lifetime Measurements of the D 1Π State of HfS and the b 3Π1 State of HfO
Open this publication in new window or tab >>Lifetime Measurements of the D 1Π State of HfS and the b 3Π1 State of HfO
2002 In: Journal of Molecular Spectroscopy, ISSN 0022-2552, Vol. 216, no 1, 131-135 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-24045 (URN)
Note
Part of urn:nbn:se:su:diva-650Available from: 2005-09-12 Created: 2005-09-12Bibliographically approved
3. A comment on Hönl-London factors
Open this publication in new window or tab >>A comment on Hönl-London factors
2005 (English)In: Journal of Molecular Spectroscopy, ISSN 0022-2852, E-ISSN 1096-083X, Vol. 233, no 2, 169-173 p.Article in journal (Refereed) Published
Abstract [en]

The literature on the Hönl-London factors of diatomic molecules, the factors in intensity formulas dependent on the rotational quantum numbers, is somewhat confused for the case of perpendicular transitions. We derive a formula, Eq. (23), for allowed singlet–singlet transitions between levels of definite parity, and show that it is consistent with standard sum rules. As an illustration, the formula is applied to the calculation of lifetimes in the B1Πu state of Na2, showing that the corrected formula gives results in good agreement with experimental measurements.

Place, publisher, year, edition, pages
Elsevier Inc., 2005
Keyword
Hönl-London factors; Lifetimes
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-24046 (URN)10.1016/j.jms.2005.06.009 (DOI)
Note
Part of urn:nbn:se:su:diva-650Available from: 2005-09-12 Created: 2005-09-12 Last updated: 2017-12-13Bibliographically approved
4. Measurement of the X 1Σg+ → A 1Σu+ of Na2 Transition Dipole Moment by Autler Townes Splitting: Comparison of Three and Four Level System Excitation Schemes
Open this publication in new window or tab >>Measurement of the X 1Σg+ → A 1Σu+ of Na2 Transition Dipole Moment by Autler Townes Splitting: Comparison of Three and Four Level System Excitation Schemes
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Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-24047 (URN)
Note
Part of urn:nbn:se:su:diva-650Available from: 2005-09-12 Created: 2005-09-12 Last updated: 2010-01-13Bibliographically approved
5. Electromagnetically Induced Transparency in Open Molecular Systems
Open this publication in new window or tab >>Electromagnetically Induced Transparency in Open Molecular Systems
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In: Opt. Commun.Article in journal (Refereed) Submitted
Identifiers
urn:nbn:se:su:diva-24048 (URN)
Note
Part of urn:nbn:se:su:diva-650Available from: 2005-09-12 Created: 2005-09-12Bibliographically approved
6. The Role of Doppler Broadening in Electromagnetically Induced Transparency and Autler-Townes Splitting in Open Molecular systems
Open this publication in new window or tab >>The Role of Doppler Broadening in Electromagnetically Induced Transparency and Autler-Townes Splitting in Open Molecular systems
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In: Phys. Rev. Lett.Article in journal (Refereed) Submitted
Identifiers
urn:nbn:se:su:diva-24049 (URN)
Note
Part of urn:nbn:se:su:diva-650Available from: 2005-09-12 Created: 2005-09-12Bibliographically approved

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