445 research outputs found
Adaptive dual-comb spectroscopy in the green region
Dual-comb spectroscopy is extended to the visible spectral range with a
set-up based on two frequency-doubled femtosecond ytterbium-doped fiber lasers.
The dense rovibronic spectrum of iodine around 19240 cm-1 is recorded within 12
ms at Doppler-limited resolution with a simple scheme that only uses
free-running femtosecond lasers
An Iterative Reconstruction Algorithm for Faraday Tomography
Faraday tomography offers crucial information on the magnetized astronomical
objects, such as quasars, galaxies, or galaxy clusters, by observing its
magnetoionic media. The observed linear polarization spectrum is inverse
Fourier transformed to obtain the Faraday dispersion function (FDF), providing
us a tomographic distribution of the magnetoionic media along the line of
sight. However, this transform gives a poor reconstruction of the FDF because
of the instrument's limited wavelength coverage. The current Faraday tomography
techniques' inability to reliably solve the above inverse problem has
noticeably plagued cosmic magnetism studies. We propose a new algorithm
inspired by the well-studied area of signal restoration, called the
Constraining and Restoring iterative Algorithm for Faraday Tomography (CRAFT).
This iterative model-independent algorithm is computationally inexpensive and
only requires weak physically-motivated assumptions to produce high fidelity
FDF reconstructions. We demonstrate an application for a realistic synthetic
model FDF of the Milky Way, where CRAFT shows greater potential over other
popular model-independent techniques. The dependence of observational frequency
coverage on the various techniques' reconstruction performance is also
demonstrated for a simpler FDF. CRAFT exhibits improvements even over
model-dependent techniques (i.e., QU-fitting) by capturing complex multi-scale
features of the FDF amplitude and polarization angle variations within a
source. The proposed approach will be of utmost importance for future cosmic
magnetism studies, especially with broadband polarization data from the Square
Kilometre Array and its precursors. We make the CRAFT code publicly available.Comment: Accepted for publication in MNRAS. 13 pages and 12 figure
Superdeformation in Asymmetric NZ Nucleus Ar
A rotational band with five -ray transitions ranging from 2 to
12 states was identified in Ar. This band is linked through
transitions from the excited 2, 4 and 6 levels to
the low-lying states; this determines the excitation energy and the spin-parity
of the band. The deduced transition quadrupole moment of 1.45 indicates that the band has a superdeformed shape. The nature of the band
is revealed by cranked Hartree--Fock--Bogoliubov calculations and a
multiparticle--multihole configuration is assigned to the band
Decay Properties of Bh and Db Produced in the Cm + Na Reaction
Decay properties of an isotope Bh and its daughter nucleus Db
produced by the Cm(Na, 5\textit{n}) reaction were studied by
using a gas-filled recoil separator coupled with a position-sensitive
semiconductor detector. Bh was clearly identified from the correlation
of the known nuclide, Db. The obtained decay properties of Bh
and Db are consistent with those observed in the 113 chain,
which provided further confirmation of the discovery of 113.Comment: Accepted for publication in J. Phys. Soc. JPN., to be published in
Vol.78 No.
Raman-induced Kerr-effect dual-comb spectroscopy
We report on the first demonstration of nonlinear dual-frequency-comb
spectroscopy. In multi-heterodyne femtosecond Raman-induced Kerr-effect
spectroscopy, the Raman gain resulting from the coherent excitation of
molecular vibrations by a spectrally-narrow pump is imprinted onto the
femtosecond laser frequency comb probe spectrum. The birefringence signal
induced by the nonlinear interaction of these beams and the sample is
heterodyned against a frequency comb local oscillator with a repetition
frequency slightly different from that of the comb probe. Such time-domain
interference provides multiplex access to the phase and amplitude Raman spectra
over a broad spectral bandwidth within a short measurement time. Experimental
demonstration, at a spectral resolution of 200 GHz, a measurement time of 293
{\mu}s and a sensitivity of 10^-6, is given on liquid samples exhibiting a C-H
stretch Raman shift.Comment: 7 pages, 4 figure
Change of nuclear configurations in the neutrinoless double- decay of Te Xe and Xe Ba
The change in the configuration of valence protons between the initial and
final states in the neutrinoless double- decay of Te
Xe and of Xe Ba has been
determined by measuring the cross sections of the (,He) reaction with
101-MeV deuterons. Together with our recent determination of the relevant
neutron configurations involved in the process, a quantitative comparison with
the latest shell-model and interacting-boson-model calculations reveals
significant discrepancies. These are the same calculations used to determine
the nuclear matrix elements governing the rate of neutrinoless double-
decay in these systems.Comment: 10 pages, 4 figures, 9 table
Adaptive real-time dual-comb spectroscopy
With the advent of laser frequency combs, coherent light sources that offer
equally-spaced sharp lines over a broad spectral bandwidth have become
available. One decade after revolutionizing optical frequency metrology,
frequency combs hold much promise for significant advances in a growing number
of applications including molecular spectroscopy. Despite its intriguing
potential for the measurement of molecular spectra spanning tens of nanometers
within tens of microseconds at Doppler-limited resolution, the development of
dual-comb spectroscopy is hindered by the extremely demanding high-bandwidth
servo-control conditions of the laser combs. Here we overcome this difficulty.
We experimentally demonstrate a straightforward concept of real-time dual-comb
spectroscopy, which only uses free-running mode-locked lasers without any
phase-lock electronics, a posteriori data-processing, or the need for expertise
in frequency metrology. The resulting simplicity and versatility of our new
technique of adaptive dual-comb spectroscopy offer a powerful transdisciplinary
instrument that may spark off new discoveries in molecular sciences.Comment: 10 pages, 5 figure
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