65 research outputs found
CAVITY-ENHANCED PARITY-NONCONSERVING OPTICAL ROTATION IN Hg, Xe, AND I
No full textAuthor Institution: Department of Physics, University of Crete, and Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas 71110 Heraklion-Crete, GreeceAtomic parity-nonconservation (PNC) experiments provide a low-energy test of the Standard Model. However, atomic PNC experiments have proved to be very difficult, typically taking at least 10-20 years to complete. In addition, the measurements of anapole moments in Cs and Tl (the only such measurements to date, performed in the mid 1990s) appear to be inconsistent with each other. Atomic PNC experiments on radioactive isotopes of Fr and Ra are underway at collider facilities (TRIUMF and KVI Groningen, respectively), for which larger experimental signals are expected and several isotopes are available. Here, we describe our recent proposals for the measurement of PNC optical rotation in metastable Hg and Xe [1], and ground state I atoms [2]. A novel optical cavity is proposed which amplifies the optical rotation by about , and allows two signal reversals, therefore allowing room-temperature, table-top PNC experiments with large experimental PNC signals, and rapid signal reversals. We discuss the experimental sensitivity to anapole moments for odd-proton nuclei (in I) and odd-neutron nuclei (in Hg and Xe). \begin{itemize} \item[1] L. Bougas, G. E. Katsoprinakis, W. von Klitzing, J. Sapirstein, and T. P. Rakitzis, Phys. Rev. Lett {\bf 108}, 210801 (2012). \item[2] G. E. Katsoprinakis, L. Bougas, T. P. Rakitzis, V. A. Dzuba and V. V. Flambaum, Phys. Rev. A ({\it submitted}) http://arxiv.org/abs/1301.6947. \end{itemize
Development of polarized sources based on molecular photodissociation
No full textMolecular photodissociation is an innovative method for the preparation of polarized atoms andmolecules. It is a fundamental chemical process that involves the absorption of one or morepolarized photons by a molecule including its fragmentation into polarized atomic (or molecular)fragments. Recently, T. P. Rakitzis’ group produced high densities of spin-polarized hydrogenatoms applying molecular photodissociation to hydrogen halides. The obtained densities (10^19cm^−3) and short production times (ns timescales) surpass by several orders of magnitude conven-tional methods such as spin-exchange optical pumping and Stern-Gerlach spin separation. Thesedensity and time regimes make it an ideal candidate for a broad range of applications, e.g., laser-induced acceleration from polarized gas targets and polarized five-nucleon fusion reactions (d-3H,d-3He). The second has been shown to have an increased cross section by ∼50% compared to theunpolarized case. The photodissociation method has been adopted by M. Büscher’s group for theproduction of polarized proton and deuteron beams at the Forschungszentrum Jülich. Here, wereport on the production and detection scheme of these beams
A Nanosecond-resolved Ultrahigh-density Spin-polarized Hydrogen Magnetometer
No full textWe introduce a novel and sensitive ns-resolved atomic magnetometer, which is at least three orders of magnitude faster than conventional magnetometers. The magnetic field dependence of hyperfine beating of high-density spin-polarized H atoms, produced from the rapid photodissociation of HCl gas with sub-ns laser pulses, results in a few nT sensitivity for a spin-projection limited sensor with 10 nl measurement volume after 1 ns measurement time. The magnetometer will allow ultrafast continuous B-field measurements in many fields, including spin chemistry, spin physics, and plasma physics.Made available in DSpace on 2021-09-24T21:09:53Z (GMT). No. of bitstreams: 2
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Previous issue date: 2021-06-2
Photofragment angular momentum distributions in the molecular frame. III. Coherent effects in the photodissociation of polyatomic molecules with circularly polarized light
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Parent–molecule rotational depolarization of photofragment angular momentum distributions: diatomic and polyatomic molecules
No full textPhotochemie kleiner Moleküle
No full textNiederjohann B. Photochemistry of small molecules. Bielefeld (Germany): Bielefeld University; 2004.The dissertation consists of two parts, where part I deals with the realization of the OH+D2 reaction and part II with the dissociation dynamics of iodine molecule above the first ionization limit.
Part I deals with the realization of the OH+D2 to HOD+D reaction. The main issue was to build a source of OH radicals with a sufficient high kinetic energy to overcome the barrier to the reaction of 5.3 kcal/mol. The OH radicals were produced by photolysis of a suitable precursor. Within this work, the OH radicals from two different precursors, H2O2 and HNO3, were studied concerning their rotational and thus their kinetic energy distribution. Also the total amount of OH radicals were compared, regarding the different precursors and also different molecular beam set-ups.
Part II deals with the photodissociation dynamics of the iodine molecule at excitation energies (10.2-20.4eV) above the first ionization threshold (9.31eV). This processes were studied with velocity map imaging, a special form of ion imaging. An analysis of the measured images showed that a variety of different processes were involved, among them production of free ion pair states, neutral dissociation of the iodine molecule and dissociation to a neutral iodine atom and an iodine ion via direct ionization to a repulsive ionic molecular state. A new process was found at excitation energies around 14eV which was attributed to a three-body-process, where the electron can take away a variable amount of kinetic energy, resulting in a very broad kinetic energy distribution of the I and I+ fragments. Coupling of a molecular Rydberg state which converges to a higher lying repulsive state of the iodine ionic molecule to a lower lying repulsive ionic molecular state is supposed to be the key mechanism.
Also a photoelectron spectrum was measured
Photofragment angular momentum distributions in the molecular frame: Determination and interpretation
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Measurement of state-resolved differential cross-sections of bimolecular reactions using single beam velocity mapping
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