25 research outputs found
Power-law intensity distribution in -decay cascades -- Nuclear Structure as a Scale-Free Random Network
By modeling the transition paths of the nuclear -decay cascade using
a scale-free random network, we uncover a universal power-law distribution of
-ray intensity , with the -ray
intensity of each transition. This property is consistently observed for all
datasets with a sufficient number of -ray intensity entries in the
National Nuclear Data Center database, regardless of the reaction type or
nuclei involved. In addition, we perform numerical simulations which support
the model's predictions of level population density
A Simple Explanation for the Observed Power Law Distribution of Line Intensity in Complex Many-Electron Atoms
It has long been observed that the number of weak lines from many-electron
atoms follows a power law distribution of intensity. While computer simulations
have reproduced this dependence, its origin has not yet been clarified. Here we
report that the combination of two statistical models -- an exponential
increase in the level density of many-electron atoms and local thermal
equilibrium of the excited state population -- produces a surprisingly simple
analytical explanation for this power law dependence. We find that the exponent
of the power law is proportional to the electron temperature. This dependence
may provide a useful diagnostic tool to extract the temperature of plasmas of
complex atoms without the need to assign lines
Power-Law Intensity Distribution of γ-Decay Cascades: Nuclear Structure as a Scale-Free Random Network
By modeling the transition paths of the nuclear γ-decay cascade using a scale-free random network, we uncover a universal power-law distribution of γ-ray intensity ρI(I)∝I⁻², with I the γ-ray intensity of each transition. This property is consistently observed for all datasets with a sufficient number of γ-ray intensity entries in the National Nuclear Data Center database, regardless of the reaction type or nuclei involved. In addition, we perform numerical simulations that support the model’s predictions of level population density
Precision measurement of the 5 2S1/2 - 4 2D5/2 quadrupole transition isotope shift between 88Sr+ and 86Sr+
We have measured the isotope shift of the narrow quadrupole-allowed 5 2S1/2 -
4 2D5/2 transition in 86Sr+ relative to the most abundant isotope 88Sr+. This
was accomplished using high-resolution laser spectroscopy of individual trapped
ions, and the measured shift is Delta-nu_meas^(88,86) = 570.281(4) MHz. We have
also tested a recently developed and successful method for ab-initio
calculation of isotope shifts in alkali-like atomic systems against this
measurement, and our initial result of Delta-nu_calc^(88,86) = 457(28) MHz is
also presented. To our knowledge, this is the first high precision measurement
and calculation of that isotope shift. While the measurement and the
calculation are in broad agreement, there is a clear discrepancy between them,
and we believe that the specific mass shift was underestimated in our
calculation. Our measurement provides a stringent test for further refinements
of theoretical isotope shift calculation methods for atomic systems with a
single valence electron
Precision isotope shift measurements in Ca using highly sensitive detection schemes
We demonstrate an efficient high-precision optical spectroscopy technique for
single trapped ions with non-closed transitions. In a double-shelving
technique, the absorption of a single photon is first amplified to several
phonons of a normal motional mode shared with a co-trapped cooling ion of a
different species, before being further amplified to thousands of fluorescence
photons emitted by the cooling ion using the standard electron shelving
technique. We employ this extension of the photon recoil spectroscopy technique
to perform the first high precision absolute frequency measurement of the
D P transition in Ca,
resulting in a transition frequency of kHz.
Furthermore, we determine the isotope shift of this transition and the
S P transition for Ca,
Ca and Ca ions relative to Ca with an
accuracy below 100 kHz. Improved field and mass shift constants of these
transitions as well as changes in mean square nuclear charge radii are
extracted from this high resolution data
Nuclear charge radii of silicon isotopes
The nuclear charge radius of Si was determined using collinear laser
spectroscopy. The experimental result was confronted with ab initio nuclear
lattice effective field theory, valence-space in-medium similarity
renormalization group, and mean field calculations, highlighting important
achievements and challenges of modern many-body methods. The charge radius of
Si completes the radii of the mirror pair Ar - Si, whose
difference was correlated to the slope of the symmetry energy in the
nuclear equation of state. Our result suggests \,MeV, which agrees
with complementary observables
Search for new bosons with ytterbium isotope shifts
The Standard Model of particle physics describes the properties of elementary
particles and their interactions remarkably well, but in particular does not
account for dark matter. Isotope-shift spectroscopy is a sensitive probe of
fifth forces and new particles that illuminate the dark matter sector. This
method sets bounds on new bosons that couple neutrons and electrons with masses
in the keV/c2 to MeV/c2 range. With increasing spectroscopic precision, such
searches are limited by uncertainties of isotope masses and the understanding
of nuclear structure. Here, we report on high-precision mass-ratio and
isotope-shift measurements of the ytterbium isotopes Yb
that exceed previous measurements by up to two orders of magnitude. From these
measurements, we extract higher-order changes in the nuclear charge
distribution along the Yb isotope chain and use these to benchmark novel ab
initio calculations. Our measurements set new bounds on the existence of the
proposed boson