14 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
Photofragment angular momentum distributions from oriented and aligned polyatomic molecules: beyond the axial recoil limit
No full textAbstract: A semi-classical theoretical treatment is presented for the description of photofragment polarization in the molecular frame, from the non-axial photodissociation of molecules which are oriented in the laboratory frame. Explicit expressions which quantify the experimental sensitivity to each of the a(q)(k)(i) polarization parameters, for prompt photodissociation, are given in terms of the non-axial-recoil deflection angles chi, alpha and phi(mu d) (which describe the orientation of the dipole and transition dipole moments about the recoil velocity), and the degree of the parent orientation and alignment. The application of this approach for the extraction of important dynamical information in the molecular frame is discussed, including cases where this information cannot be measured for isotropic samples of parent molecules
Photochemie 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
Measurement of photofragment polarization: Interference effects in state-selected polyatomic molecules.
No full textMolecular frame properties from photodissociation of laboratory-oriented symmetric top and chiral molecules
No full text
Directional dynamics in the photodissociation of oriented molecules
No full textWe observed directional dynamics in the photodissociation of an oriented molecule. When a laser dissociated hexapole-oriented carbonyl sulfide molecules, the three-dimensional recoil of carbon monoxide fragments, which we measured with ion imaging, was strongly asymmetric. We obtained a microscopic view of molecular bond breaking that revealed both the sign and the magnitude of the deflection angle of the fragment in the molecular frame. This experimental approach can be applied to study and control the three-dimensional dynamics of photoinitiated reactions of fixed molecules or molecules oriented by emerging techniques
Photofragment alignment in the photodissociation of I-2 from 450 to 510 nm
No full textContains fulltext :
35565.pdf (Publisher’s version ) (Open Access)A combination of velocity map imaging and slicing techniques have been used to measure the product recoil anisotropy and angular momentum polarization for the photodissociation process I-2-> I(P-2(3/2))+I(P-2(3/2)) and I-2-> I(P-2(3/2))+I(P-2(1/2)) in the 450-510 nm laser wavelength region using linearly polarized photolysis and probe laser light. The former channel is produced predominantly via perpendicular excitation to the (1)Pi(u) state, and the latter is predominantly parallel, via the B (3)Pi(0(u))(+) state. In both cases we observe mostly adiabatic dissociation, which produces electronically aligned iodine atoms in the parallel to m parallel to=1/2 states with respect to the recoil direction. (c) 2006 American Institute of Physics
Towards the complete experiment: Measurement of s((1)d(2)) polarization in correlation with single rotational states of co(j) from the photodissociation of oriented ocs(v(2)=1 vertical bar jlm=111)
No full textContains fulltext :
92507.pdf (Publisher’s version ) (Open Access)11 p
Molecular and laboratory frame photofragment angular distributions from oriented and aligned molecules
No full textWe present explicit expressions for the molecular frame and laboratory frame photofragment angular distributions from oriented parent molecules, in terms of the dynamically significant molecular frame angles between the recoil direction and the transition and permanent dipole moments of the molecule. We discuss how these angles can be measured from distinct experimental geometries. Explicit examples are given on the extracted information of the molecular frame photodissociation, especially in case of non-axial recoil dynamics. © 2003 Elsevier Science B.V. All rights reserved
