Search results for "atomic and molecular physics"
showing 10 items of 4501 documents
Theory and implications of neutrino mass
1989
Abstract I briefly review the basic theory of neutrino mass from the point of view of modern gauge theories. Some of the implications of neutrino masses for particle physics, nuclear physics, cosmology and astrophysics are discussed.
Collisional relaxation measurements on Pb+ hyperfine levels
1993
The time constants for population relaxation of optically pumped Pb+ ions in a Paul ion trap have been determined in a He buffer gas atmosphere with additional components of other gases. For the 6P1/2 ground state of Pb+ and an ion temperatur of 104 K we find cross sections of 0.72(0.33)·10−17 cm2; 0.59(0.38)·10−15 cm2; and 2.56(0.74)·10−14 cm2 for He, N2 and O2, respectively. The error includes an estimated 20% uncertaincy in the pressure calibration of a residual gas analyser.
Nano photoelectron ioniser chip using LaB6 for ambient pressure trace gas detection
2012
A detector including a nanoscaled ioniser chip that surmounts the limitation of conventional photo ionisation detectors is presented. Here, ionisable gaseous substances can be detected by photoelectrons accelerated to the ionisation potential of the incoming gaseous molecules. Thin lanthanum hexaboride (LaB"6) films deposited by pulsed laser technique (PLD) serve as the air stable photocathode material representing the basis of the ioniser chip of the detector. Besides the analysis of the emission behaviour of the photocathode in vacuum and at atmospheric pressure, the detection of different volatile alcohols using the detector with a low-energy UV LED instead of a PID (VUV photon source) w…
High-order harmonic generation via bound-bound transitions in an elliptically polarized laser field
2016
We use a simplified five-level system to investigate the high-order harmonic generation (HHG) spectrum emitted by an atom driven by a linearly or elliptically polarized laser field. For this model, the Schrödinger equation is exactly analytically reduced to the system of ordinary differential equations, which is solved numerically. Studying the intensity and polarization of the emitted radiation, we find that under high laser ellipticity the harmonic emission is suppressed. However, the harmonic intensity typically depends nonmonotonously on the laser ellipticity. Such anomalous behavior is very pronounced for the resonant harmonic. We offer an explanation of this behavior based on the incr…
Dressed emitters as impurities
2021
Dressed states forming when quantum emitters or atoms couple to a photonic bath underpin a number of phenomena and applications, in particular dispersive effective interactions occurring within photonic bandgaps. Here, we present a compact formulation of the resolvent-based theory for calculating atom-photon dressed states built on the idea that the atom behaves as an effective impurity. This establishes an explicit connection with the standard impurity problem in condensed matter. Moreover, it allows us to formulate and settle in a model-independent context a number of properties previously known only for specific models or not entirely formalized. The framework is next extended to the cas…
Precision atomic physics techniques for nuclear physics with radioactive beams
2012
Atomic physics techniques for the determination of ground-state properties of radioactive isotopes are very sensitive and provide accurate masses, binding energies, Q-values, charge radii, spins, and electromagnetic moments. Many fields in nuclear physics benefit from these highly accurate numbers. They give insight into details of the nuclear structure for a better understanding of the underlying effective interactions, provide important input for studies of fundamental symmetries in physics, and help to understand the nucleosynthesis processes that are responsible for the observed chemical abundances in the Universe. Penning-trap and and storage-ring mass spectrometry as well as laser spe…
Quantum localization and bound state formation in Bose-Einstein condensates
2010
We discuss the possibility of exponential quantum localization in systems of ultracold bosonic atoms with repulsive interactions in open optical lattices without disorder. We show that exponential localization occurs in the maximally excited state of the lowest energy band. We establish the conditions under which the presence of the upper energy bands can be neglected, determine the successive stages and the quantum phase boundaries at which localization occurs, and discuss schemes to detect it experimentally by visibility measurements. The discussed mechanism is a particular type of quantum localization that is intuitively understood in terms of the interplay between nonlinearity and a bou…
Resonance ionization spectroscopy of thorium isotopestowards a laser spectroscopic identification of the low-lying 7.6 eV isomer of 229Th
2011
International audience; In-source resonance ionization spectroscopy was used to identify an efficient and selective three step excitation/ionization scheme of thorium, suitable for titanium:sapphire (Ti:sa) lasers. The measurements were carried out in preparation of laser spectroscopic investigations for an identification of the low-lying 229 m Th isomer predicted at 7.6 ± 0.5 eV above the nuclear ground state. Using a sample of 232 Th, a multitude of optical transitions leading to over 20 previously unknown intermediate states of even parity as well as numerous high-lying odd parity auto-ionizing states were identified. Level energies were determined with an accuracy of 0.06 cm −1 for inte…
First-principles nonequilibrium Green's-function approach to transient photoabsorption: Application to atoms
2015
We put forward a first-principle NonEquilibrium Green's Function (NEGF) approach to calculate the transient photoabsorption spectrum of optically thin samples. The method can deal with pump fields of arbitrary strength, frequency and duration as well as for overlapping and nonoverlapping pump and probe pulses. The electron-electron repulsion is accounted for by the correlation self-energy, and the resulting numerical scheme deals with matrices that scale quadratically with the system size. Two recent experiments, the first on helium and the second on krypton, are addressed. For the first experiment we explain the bending of the Autler-Townes absorption peaks with increasing the pump-probe d…
Searching for alignment-to-orientation conversion in the ground state of atomic Cs with circularly polarized laser probe
2020
In this study we explored the possibilities for observing the angular momentum alignment-to-orientation conversion (AOC) in the ground state of various alkali metals: K, Rb, Cs. For theoretical analysis we used a model that is based on the Optical Bloch equations for the density matrix. Our model includes the interaction of all neighboring hyperfine levels with laser radiation, the mixing of magnetic sublevels in an external magnetic field, the coherence properties of the exciting laser radiation, and the Doppler effect. Additionally we simulated signals where the ground- or the excited-state coherent processes were numerically switched off in order to determine the origins of the features …