409 research outputs found
The CO A-X System for Constraining Cosmological Drift of the Proton-Electron Mass Ratio
The band system of carbon monoxide,
which has been detected in six highly redshifted galaxies (), is
identified as a novel probe method to search for possible variations of the
proton-electron mass ratio () on cosmological time scales. Laboratory
wavelengths of the spectral lines of the A-X (,0) bands for have
been determined at an accuracy of
through VUV Fourier-transform absorption spectroscopy, providing a
comprehensive and accurate zero-redshift data set. For the (0,0) and (1,0)
bands, two-photon Doppler-free laser spectroscopy has been applied at the accuracy level, verifying the absorption data. Sensitivity
coefficients for a varying have been calculated for the CO A-X
bands, so that an operational method results to search for -variation.Comment: 7 pages (main article), 3 figures, includes supplementary materia
Novel techniques in VUV high-resolution spectroscopy
Novel VUV sources and techniques for VUV spectroscopy are reviewed.
Laser-based VUV sources have been developed via non-linear upconversion of
laser pulses in the nanosecond (ns), the picosecond (ps), and femtosecond (fs)
domain, and are applied in high-resolution gas phase spectroscopic studies.
While the ns and ps pulsed laser sources, at Fourier-transform limited
bandwidths, are used in wavelength scanning spectroscopy, the fs laser source
is used in a two-pulse time delayed mode. In addition a Fourier-transform
spectrometer for high resolution gas-phase spectroscopic studies in the VUV is
described, exhibiting the multiplex advantage to measure many resonances
simultaneously.Comment: 17 Pages, 8 figures, Conference proceedings of the VUV/X-ray 2013 at
Hefei, Chin
High-resolution Fourier-transform XUV photoabsorption spectroscopy of 14N15N
The first comprehensive high-resolution photoabsorption spectrum of 14N15N
has been recorded using the Fourier-transform spectrometer attached to the
Desirs beamline at the Soleil synchrotron. Observations are made in the extreme
ultraviolet (XUV) and span 100,000-109,000 cm-1 (100-91.7 nm). The observed
absorption lines have been assigned to 25 bands and reduced to a set of
transition energies, f values, and linewidths. This analysis has verified the
predictions of a theoretical model of N2 that simulates its photoabsorption and
photodissociation cross section by solution of an isotopomer independent
formulation of the coupled-channel Schroedinger equation. The mass dependence
of predissociation linewidths and oscillator strengths is clearly evident and
many local perturbations of transition energies, strengths, and widths within
individual rotational series have been observed.Comment: 14 pages, 8 figures, one data archiv
Oscillator strengths for transitions to Rydberg levels in , and between 967 and 972 A
Absorption oscillator strengths have been determined from high-resolution
spectra in the 967-972 \AA region of three CO isotopomers for transitions to
the Rydberg levels 4{\it p}(0), 3{\it d}(1) and 4{\it p}(0),
as well as to the mixed {\it E(6)} level recently characterized by Eidelsberg
et al. (2004). Synchrotron radiation from the Super-ACO electron storage ring
at Orsay (LURE) was used as a light source. Oscillator strengths were extracted
from the recorded spectra by least-squares fitting of the experimental profiles
with synthetic spectra taking into account the homogeneous and heterogeneous
interactions of the four levels. Column densities were derived from fits to the
3{\it p}(0) absorption band whose oscillator strength is well established.
These are the first reported measurements for CO. For
CO, our results are consistent with the larger values obtained in
the most recent laboratory and astronomical studies.Comment: 9 pages 7 figures 3 tables. Accepted in A&A, date of acceptance
11/05/200
High-Resolution Oscillator Strength Measurements of the v\u27 = 0,1 Bands of the B-X, C-X, and E-X Systems in Five Isotopologues of Carbon Monoxide
We report oscillator strengths for six strong vibrational bands between 105.0 and 115.2 nm, associated with transitions from the v = 0 level of the X 1Σ+ ground state to the v = 0 and 1 levels of the B 1Σ+, C 1Σ+, and E 1Π states, in 12C16O, 12C17O, 12C18O, 13C16O, and 13C18O. These measurements extend the development of a comprehensive database of line positions, oscillator strengths, and linewidths of photodissociating transitions for all astrophysically relevant CO isotopologues. The E–X bands, in particular, play central roles in CO photodissociation and fractionationmodels of interstellar clouds and circumstellar disks including the early solar nebula. The resolving powers of the room-temperature measurements, R = 300,000–400,000, allow for the analysis of individual line strengths within bands; the measurements reveal J-dependences in the branch intensities of the C(v = 0,1)–X(0) and E(v = 0,1)–X(0) bands in all isotopologues. Minimal or no isotopologue dependence was found in the f-values of the C(v = 0,1)–X(0) and E(v = 0,1)–X(0) bands at a ∼5% uncertainty level. Revised dissociation branching ratios for the C(v = 0,1) and E(v = 0,1) levels are computed based on these f-values. The weak isotopologue dependence of the f-values presented here eliminates this mechanism as an explanation for the large 17O enrichments seen in recent laboratory photolysis experiments on CO at wavelengths from 105 to 108 nm
Hydrolysis of rat melanin-concentrating hormone by endopeptidase 24.11 (neutral endopeptidase)
VUV Angle-resolved Photoelectron Spectroscopy on Isolated Hybrid Nanostructures
Aerosol photoemission spectroscopy became an important method for studying electronic structure of submicrometer particles without the influence of substrate [1]. It comprises irradiation of the focused particle beam by either vacuum-ultraviolet (VUV) or soft x-ray radiation under high vacuum conditions and subsequent detection and discrimination of the photoelectrons according to their kinetic energies and momenta [2-4]. As intermediates between atoms or molecules and macroscopic matter, nanometer-sized objects exhibit specific electronic and transport properties that strongly depend on their size, morphology and surface chemistry. Modification of nanoparticle surfaces by conjugation with molecules presents a convenient method of altering a wide range of physicochemical characteristics of the nanomaterials, which does not require development of new synthetic procedures. Furthermore, by a proper choice of molecules used in surface modification, additional properties of the hybrid nanostructures can be achieved, which could not be found in the starting materials. In this lecture, we will present the selected results of our investigations on hybrid nanostructures comprised of noble metal and metal oxide nanomaterials functionalized by biologically relevant molecules. Particular attention will be given to the vacuum-ultraviolet angle-resolved photoelectron spectroscopy (VUV ARPES) studies on isolated functionalized nanosystems performed at the DESIRS beamline. The emergence of the photoelectron circular dichroism in hybrid nanoparticles will be briefly discussed.VII International School and Conference on Photonics : PHOTONICA2019 : Abstracts of Tutorial, Keynote, Invited Lectures, Progress Reports and Contributed Papers; August 26-30; Belgrad
Synchrotron radiation photoemission spectroscopy study of the valence band electronic structure of Ag-Ag2S Janus nanoparticles for the development of nanomotors propelled by NIR light
Silver-silver sulfide (Ag-Ag2S) hybrid nanosystem which consists of plasmonic metal Ag and narrow band gap semiconductor Ag2S is typically studied as a photocatalyst under visible and NIR light [1,2]. Janus morphology of this system is especially interesting due to the possibility of initiating two different chemical reactions that are spatially separated on two halves of the system. Here, we present the fabrication of Ag-Ag2S Janus nanoparticles and the examination of their valence electronic structure. For the investigation of the electronic structure of isolated nanoparticles, we performed synchrotron radiation vacuum ultraviolet photoelectron spectroscopy using the velocity map imaging (VMI) technique. By using two different photon energies, hν = 9.5 eV and hν = 11 eV, we obtained angle-resolved photoelectron images. Photoemission spectra and the dependence of the asymmetry parameter α on the binding energy are derived from VMI images using modified p-Basex inversion method [3]. In addition, we coupled Ag-Ag2S nanoparticles to the TiO2 and studied the actuation of obtained hybrid nanosystem in a liquid medium under visible and NIR light.IX International School and Conference on Photonics : PHOTONICA2023 : book of abstracts; August 28 - September 1, 2023; Belgrad
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