Search results for "dipole moment"
showing 10 items of 258 documents
Intramolecular charge transfer in elongated donor-acceptor conjugated polyenes
1995
Abstract Intramolecular charge transfer (ICT) has been investigated by electro-optical absorption measurements for two series of donor-acceptor polyenes of increasing length. Each molecule undergoes an increase in dipole moment upon photoexcitation. The experimental results indicate that lengthening the polyenic chain linking the donor and acceptor end groups results in a bathochromic shift of the ICT absorption band and induces marked increases of both excited state and transition dipoles, whereas the ground-state dipole is relatively unaffected. As a result, marked photoinduced changes in the dipole moment (up to 33 D) were obtained with the longest molecules (up to 27 A) leading to highl…
Roadmap on STIRAP applications
2019
STIRAP (stimulated Raman adiabatic passage) is a powerful laser-based method, usually involving two photons, for efficient and selective transfer of populations between quantum states. A particularly interesting feature is the fact that the coupling between the initial and the final quantum states is via an intermediate state, even though the lifetime of the latter can be much shorter than the interaction time with the laser radiation. Nevertheless, spontaneous emission from the intermediate state is prevented by quantum interference. Maintaining the coherence between the initial and final state throughout the transfer process is crucial. STIRAP was initially developed with applications in …
Observation of Gravitationally Induced Vertical Striation of Polarized Ultracold Neutrons by Spin-Echo Spectroscopy.
2015
We describe a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a $|B_0|=1~\text{\mu T}$ magnetic field. We have demonstrated that the analysis of UCN spin-echo resonance signals in combination with knowledge of the ambient magnetic field provides an excellent method by which to reconstruct the energy spectrum of a confined ensemble of neutrons. The method takes advantage of the relative dephasing of spins arising from a gravitationally induced striation of stored UCN of different energies, and also permits an improved determination of the vertical magnetic-field gradient with an exceptional accuracy of $1.1~\text{pT/cm}$. This novel combination …
Measurement of the permanent electric dipole moment of the neutron
2020
We present the result of an experiment to measure the electric dipole moment (EDM) of the neutron at the Paul Scherrer Institute using Ramsey’s method of separated oscillating magnetic fields with ultracold neutrons. Our measurement stands in the long history of EDM experiments probing physics violating time-reversal invariance. The salient features of this experiment were the use of a 199Hg comagnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic-field changes. The statistical analysis was performed on blinded datasets by two separate groups, while the estimation of systematic effects profited from an unprecedented knowledge of the magne…
Dynamic stabilization of the magnetic field surrounding the neutron electric dipole moment spectrometer at the Paul Scherrer Institute
2014
The Surrounding Field Compensation (SFC) system described in this work is installed around the four-layer Mu-metal magnetic shield of the neutron electric dipole moment spectrometer located at the Paul Scherrer Institute. The SFC system reduces the DC component of the external magnetic field by a factor of about 20. Within a control volume of approximately 2.5m x 2.5m x 3m disturbances of the magnetic field are attenuated by factors of 5 to 50 at a bandwidth from $10^{-3}$ Hz up to 0.5 Hz, which corresponds to integration times longer than several hundreds of seconds and represent the important timescale for the nEDM measurement. These shielding factors apply to random environmental noise f…
Magnetic field uniformity in neutron electric dipole moment experiments
2019
© 2019 American Physical Society. Magnetic-field uniformity is of the utmost importance in experiments to measure the electric dipole moment of the neutron. A general parametrization of the magnetic field in terms of harmonic polynomial modes is proposed, going beyond the linear-gradients approximation. We review the main undesirable effects of nonuniformities: depolarization of ultracold neutrons and Larmor frequency shifts of neutrons and mercury atoms. The theoretical predictions for these effects were verified by dedicated measurements with the single-chamber neutron electric-dipole-moment apparatus installed at the Paul Scherrer Institute. ispartof: Physical Review A vol:99 issue:4 sta…
The pulsed neutron beam EDM experiment
2018
International audience; We report on the Beam EDM experiment, which aims to employ a pulsed cold neutron beam to search for an electric dipole moment instead of the established use of storable ultracold neutrons. We present a brief overview of the basic measurement concept and the current status of our proof-of-principle Ramsey apparatus.
Tensorial Development of the Rovibronic Hamiltonian and Dipole Moment Operators for XY3Z Molecules with a Degenerate Electronic State. Preliminary Ap…
2009
Abstract We present a development of the Hamiltonian and transition moment operators of XY3Z ( C 3 v ) symmetric tops molecules in a degenerate electronic state with the aid of a tensorial formalism developed in a recent paper [A. El Hilali, V. Boudon, M. Loete, J. Mol. Spectrosc. 239 (2006) 41–50]. Electronic operators are defined from group theory properties. They provide a new approach to build an effective rovibronic Hamiltonian as well as an effective dipole moment operator for rovibronic transition of XY3Z molecules. This model is studied qualitatively thanks to the tensorial algebra properties. Expressions of the matrix elements are derived for these operators. A first simple applica…
The Role of the Low-Lying $$n\pi ^*$$ n π ∗ States on the Photophysics of Pyrazine
2016
In this chapter, the theoretical tools introduced in Chaps. 2 and 4 are applied to the study of the non-adiabatic relaxation dynamics of pyrazine after ultraviolet (UV) excitation.
A new limit of the 129 Xenon Electric Dipole Moment
2019
We report on the first preliminary result of our 129Xe EDM measurement performed by the MIXed collaboration. The aim of this report is to demonstrate the feasibility of a new method to set limits on nuclear EDMs by investigating the EDM of the diamagnetic 129Xe atoms. In our setup, hyperpolarized 3He serves as a comagnetometer needed to suppress magnetic field fluctuations. The free induction decay of the two polarized spin species is directly measured by low noise DC SQUIDs, and the weighted phase difference extracted from these measurements is used to determine a preliminary upper limit on the 129Xe EDM.