Search results for "Excitation"
showing 10 items of 1290 documents
Studies of narrow autoionizing resonances in gadolinium
2003
The autoionization (AI) spectrum of gadolinium between the first and second limits has been investigated by triple-resonance excitation with high-resolution cw lasers. A large number of narrow AI resonances have been observed and assigned total angular momentum J values. The resonances are further divided into members of AI Rydberg series converging to the second limit or other ''interloping'' levels. Fine structure in the Rydberg series has been identified and interpreted in terms of Jc j coupling. A number of detailed studies have been performed on the interloping resonances: These include lifetime determination by lineshape analysis, isotope shifts, hyperfine structure, and photoionizati…
Experimental verification of position-dependent angular-momentum selection rules for absorption of twisted light by a bound electron
2018
We analyze the multipole excitation of atoms with twisted light, i.e., by a vortex light field that carries orbital angular momentum. A single trapped $^{40}$Ca$^+$ ion serves as a localized and positioned probe of the exciting field. We drive the $S_{1/2} \to D_{5/2}$ transition and observe the relative strengths of different transitions, depending on the ion's transversal position with respect to the center of the vortex light field. On the other hand, transition amplitudes are calculated for a twisted light field in form of a Bessel beam, a Bessel-Gauss and a Gauss-Laguerre mode. Analyzing experimental obtained transition amplitudes we find agreement with the theoretical predictions at a…
Anthracene Fluorescence Quenching by a Tetrakis (Ketocarboxamide) Cavitand
2014
Quenching of both fluorescence lifetime and fluorescence intensity of anthracene was investigated in the presence of a newly derived tetrakis (ketocarboxamide) cavitand at various concentrations. Time-correlated single photon counting method was applied for the lifetime measurements. A clear correlation between the fluorescence lifetime of anthracene as a function of cavitand concentration in dimethylformamide solution was observed. The bimolecular collisional quenching constant was derived from the decrease of lifetime. Fluorescence intensity was measured in the emission wavelength region around 400 nm as a result of excitation at 280 nm. Effective quenching was observed in the presence of…
Intramolecular electronic excitation energy transfer in donor∕acceptor dyads studied by time and frequency resolved single molecule spectroscopy
2008
Electronic excitation energy transfer has been studied by single molecule spectroscopy in donor/acceptor dyads composed of a perylenediimide donor and a terrylenediimide acceptor linked by oligo(phenylene) bridges of two different lengths. For the shorter bridge (three phenylene units) energy is transferred almost quantitatively from the donor to the acceptor, while for the longer bridge (seven phenylene units) energy transfer is less efficient as indicated by the occurrence of donor and acceptor emission. To determine energy transfer rates and efficiencies at the single molecule level, several methods have been employed. These comprise time-correlated single photon counting techniques at r…
Matrix-isolation and ab initio study of the complex between formic acid and xenon
2012
Abstract We report on the identification of the complexes of formic acid (FA) and Xe in an argon matrix. The geometries, interaction energies, reaction barriers, and vibrational spectra of the FA⋯Xe complexes are calculated at the MP2 level of theory. The calculations reveal four structures for the trans-FA⋯Xe complex and four structures for the cis-FA⋯Xe complex. In the experiments, two structures of the trans-FA⋯Xe complex are observed after deposition of FA/Xe/Ar matrices, with and without OH⋯Xe interaction (H-bonded and non-H-bonded structures). The cis-FA⋯Xe complex was synthesized by vibrational excitation of the non-H-bonded trans-FA⋯Xe complex. The non-H-bonded and H-bonded structur…
Measurements of transition probabilities for two N I infrared transitions and their application for diagnostics of low temperature plasmas
2010
Abstract Spectra emitted from a wall-stabilized arc, running in a gas mixture of helium, argon, nitrogen, oxygen and traces of hydrogen have been studied. Intensities of selected spectral transitions of neutral nitrogen and oxygen have been measured. Applying the Boltzmann plot method and using a reliable set of O I transition probabilities of spectral lines, originating from levels considerably spread in excitation energies, the temperatures of arc plasmas have been determined. Line intensities of two N I infrared transitions, originating from doubly excited terms 3p′ 2 F o and 3p′ 2 G have been measured. In order to obtain the corresponding transition probabilities ( A ki ) for these line…
Access to Gamma-ray Spectroscopy of Neutron-Rich sdfp Shell Nuclei
2000
γ-rays in neutron-rich sdfp shell nuclei, produced in deep-inelastic processes during collisions of 37Cl and 40Ar ions on 208Pb and of 48Ca ions on 48Ca, have been studied using large Ge multidetector arrays. Candidates for new yrast states in heavy argon and sulfur isotopes have been identified.
Phonon coupling of non-bridging oxygen hole center with the silica environment: Temperature dependence of the 1.9 eV emission spectra
2008
Abstract We report an experimental study on the shape of the 1.9 eV emission associated with non-bridging oxygen hole centers in silica and its temperature dependence, from 4 up to 300 K, under visible and ultraviolet excitation. Our analysis points out that these defects are coupled with their environment by phonons whose contribution can be described by the single mode of mean frequency between 300–400 cm −1 and Huang–Rhys factor of ∼3. On increasing the temperature, the luminescence intensity undergoes a thermal quenching caused by non-radiative processes, its deviation from a pure Arrhenius law can be accounted for by an uniform distribution of activation energy, from 0.002 to 0.05 eV. …
In situ detection of atomic and molecular iodine using resonance and off-resonance fluorescence by lamp excitation: ROFLEX
2018
17 pags, 11 figs, 4 tabs
Rydberg excitation of cold atoms inside a hollow core fiber
2017
We report on a versatile, highly controllable hybrid cold Rydberg atom fiber interface, based on laser cooled atoms transported into a hollow core Kagom\'{e} crystal fiber. Our experiments are the first to demonstrate the feasibility of exciting cold Rydberg atoms inside a hollow core fiber and we study the influence of the fiber on Rydberg electromagnetically induced transparency (EIT) signals. Using a temporally resolved detection method to distinguish between excitation and loss, we observe two different regimes of the Rydberg excitations: one EIT regime and one regime dominated by atom loss. These results are a substantial advancement towards future use of our system for quantum simulat…