Search results for "Spectral"
showing 10 items of 3116 documents
Total absorption γ -ray spectroscopy of the β -delayed neutron emitters Br87 , Br88 , and Rb94
2017
We investigate the decay of 87,88Br and 94Rb using total absorption γ -ray spectroscopy. These important fission products are β-delayed neutron emitters. Our data show considerable βγ intensity, so far unobserved in high-resolution γ -ray spectroscopy, from states at high excitation energy. We also find significant differences with the β intensity that can be deduced from existing measurements of the β spectrum. We evaluate the impact of the present data on reactor decay heat using summation calculations. Although the effect is relatively small it helps to reduce the discrepancy between calculations and integral measurements of the photon component for 235U fission at cooling times in the r…
Taming conformational heterogeneity in and with vibrational circular dichroism spectroscopy
2019
Chemical science 10, 7680 -7689 (2019). doi:10.1039/C9SC02866H
Analysis of high-harmonic generation in terms of complex Floquet spectral analysis
2017
Recent developments on intense laser sources is opening a new field of optical sciences. An intense coherent light beam strongly interacting with the matter causes a coherent motion of a particle, forming a strongly dressed excited particle. A photon emission from this dressed excited particle is a strong nonlinear process causing high-harmonic generation (HHG), where the perturbation analysis is broken down. In this work, we study a coherent photon emission from a strongly dressed excited atom in terms of complex spectral analysis in the extended Floquet-Hilbert-space. We have obtained the eigenstates of the total Hamiltonian with use of Feshbach-Brilloiun-Wigner projection method. In this…
Probing High Frequency Noise with Macroscopic Resonant Tunneling
2011
We have developed a method for extracting the high-frequency noise spectral density of an rf-SQUID flux qubit from macroscopic resonant tunneling (MRT) rate measurements. The extracted noise spectral density is consistent with that of an ohmic environment up to frequencies $~$4 GHz. We have also derived an expression for the MRT line shape expected for a noise spectral density consisting of such a broadband ohmic component and an additional strongly peaked low-frequency component. This hybrid model provides an excellent fit to experimental data across a range of tunneling amplitudes and temperatures.
Current-spin-density-functional study of persistent currents in quantum rings
2000
We present a numerical study of persistent currents in quantum rings using current spin density functional theory (CSDFT). This formalism allows for a systematic study of the joint effects of both spin, interactions and impurities for realistic systems. It is illustrated that CSDFT is suitable for describing the physical effects related to Aharonov-Bohm phases by comparing energy spectra of impurity-free rings to existing exact diagonalization and experimental results. Further, we examine the effects of a symmetry-breaking impurity potential on the density and current characteristics of the system and propose that narrowing the confining potential at fixed impurity potential will suppress t…
Hyperfine structure in the rotational spectra of trans-formic acid: Lamb-dip measurements and quantum-chemical calculations
2010
Context. Formic acid, HCOOH, is the simplest organic acid and the first that has been identified in the interstellar medium. Its astrophysical relevance has motivated this spectroscopic study. Aims. The aim of this investigation is to provide very accurate rest frequencies for the trans isomer of HCOOH as well as to improve the spectroscopic and hyperfine parameters available in the literature for this molecule. Methods. The Lamb-dip technique has been exploited in order to record the rotational spectrum of trans-HCOOH at sub-Doppler resolution in the millimeter- and submillimeter-wave frequency ranges and, when possible, to resolve the hyperfine structure due to the hydrogen nuclei. THz me…
AC-Stark shift and photoionization of Rydberg atoms in an optical dipole trap
2010
We have measured the AC-Stark shift of the $14D_{5/2}$ Rydberg state of rubidium 87 in an optical dipole trap formed by a focussed CO$_2$-laser. We find good quantitative agreement with the model of a free electron experiencing a ponderomotive potential in the light field. In order to reproduce the observed spectra we take into account the broadening of the Rydberg state due to photoionization. The extracted cross-section is compatible with previous measurements on neighboring Rydberg states.
Monte Carlo analysis of electronic noise in semiconductors under sub‐terahertz cyclostationary mixed fields
2006
This paper reports the results of Monte Carlo simulations of electronic noise in a GaAs bulk driven by two mixed high-frequency large-amplitude periodic electric fields. Under these conditions, the system response shows some peculiarities in the noise performance, such as a resonant-like enhancement of the spectra near the two frequencies of the applied fields. The relations among the frequency response and the velocity fluctuations as a function of intensities and frequencies of the sub-terahertz mixed excitation fields have been investigated. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Wave-mixing effects on electronic noise in semiconductors
2006
The results of a Monte Carlo analysis of hot-electron intrinsic noise in a n-type GaAs bulk driven by two mixed large-amplitude alternating electric fields having frequency in the subterahertz range are presented. The noise properties are investigated by studying the velocity autocorrelation function and the noise spectrum. We explored the relations among the frequency response and the velocity fluctuations as a function of the frequencies and intensities of the mixed fields. When the semiconductor is driven by two mixed ciclostationary electric fields, a resonant-like enhancement of the spectra near the two frequencies of the applied fields is found.
The Fučík spectrum for nonlocal BVP with Sturm–Liouville boundary condition
2014
Boundary value problem of the form x''=-μx++λx-, αx(0)+(1-α)x'(0)=0, ∫01 x(s)ds=0 is considered, where μ,λ∈ R and α∈ [0,1]. The explicit formulas for the spectrum of this problem are given and the spectra for some α values are constructed. Special attention is paid to the spectrum behavior at the points close to the coordinate origin.