Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userHigh-Resolution Laser Spectroscopy of Long-Lived Plutonium Isotopes
106
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Long-lived isotopes of plutonium were studied using two complementary techniques, high-resolution resonance ionisation spectroscopy (HR-RIS) and collinear laser spectroscopy (CLS). Isotope shifts have been measured on the $5f^67s^2 ^7F_0 rightarrow 5f^56d^27s (J=1)$ and $5f^67s^2 ^7F_1 rightarrow 5f^67s7p (J=2)$ atomic transitions using the HR-RIS method and the hyperfine factors have been extracted for the odd mass nuclei $^{239,241}$Pu. Collinear laser spectroscopy was performed on the $5f^67s ^8F_{1/2} rightarrow J=1/2; (27523.61text{cm}^{-1})$ ionic transition with the hyperfine $A$ factors measured for $^{239}$Pu. Changes in mean-squared charge radii have been extracted and show a good agreement with previous non-optical methods, with an uncertainty improvement by approximately one order of magnitude. Plutonium represents the heaviest element studied to date using collinear laser spectroscopy.
rate research
Read More
Hyperfine spectra of $^text{27-32}$Al ($Z=13$) have been measured at the ISOLDE-CERN facility via collinear laser spectroscopy using the $3s^23p ^2text{P}^text{o} _{3/2}rightarrow 3s^24s ^2text{S}_{1/2}$ atomic transition. For the first time, mean-square charge radii of radioactive aluminum isotopes have been determined alongside the previously unknown magnetic dipole moment of $^{29}$Al and electric quadrupole moments of $^{29,30}$Al. A potentially reduced charge radius at $N=19$ may suggest an effect of the $N=20$ shell closure, which is visible in the Al chain, contrary to other isotopic chains in the $sd$ shell. The experimental results are compared to theoretical calculations in the framework of the valence-space in-medium similarity renormalization group using multiple sets of two and three-nucleon forces from chiral effective field theory. While the trend of experimental magnetic dipole and electric quadrupole moments is well reproduced, the absolute values are underestimated by theory, consistent with earlier studies. Moreover, both the scale and trend of the charge radii appear to be very sensitive to the chosen interaction.
Laser spectroscopic studies on minute samples of exotic radioactive nuclei require very efficient experimental techniques. In addition, high resolving powers are required to allow extraction of nu- clear structure information. Here we demonstrate that by using weak atomic transitions, resonance laser ionization spectroscopy is achieved with the required high efficiency (1-10%) and precision (linewidths of tens of MHz). We illustrate experimentally and through the use of simulations how the narrow experimental linewidths are achieved and how distorted resonance ionization spec- troscopy lineshapes can be avoided. The role of the delay of the ionization laser pulse with respect to the excitation laser pulse is crucial: the use of a delayed ionization step permits the best resolving powers and lineshapes. A high efficiency is maintained if the intermediate level has a lifetime that is at least of the order of the excitation laser pulse width. A model that describes this process re- produces well the observed features and will help to optimize the conditions for future experiments.
The discovery of naturally occurring long-lived isomeric states (t_1/2 > 10^8 yr) in the neutron-deficient isotopes 211,213,217,218Th [A. Marinov et al., Phys. Rev. C 76, 021303(R) (2007)] was reexamined using accelerator mass spectrometry (AMS). Because AMS does not suffer from molecular isobaric background in the detection system, it is an extremely sensitive technique. Despite our up to two orders of magnitude higher sensitivity we cannot confirm the discoveries of neutron-deficient thorium isotopes and provide upper limits for their abundances.
Evidence for the existence of long-lived neutron-deficient isotopes has been found in a study of naturally-occurring Th using iductively coupled plasma-sector field mass spectrometry. They are interpreted as belonging to the recently discovered class of long-lived high spin super- and hyperdeformed isomers.
The magnetic dipole moments and changes in mean-square charge radii of the neutron-rich $^{218m,219,229,231}text{Fr}$ isotopes were measured with the newly-installed Collinear Resonance Ionization Spectroscopy (CRIS) beam line at ISOLDE, CERN, probing the $7s~^{2}S_{1/2}$ to $8p~^{2}P_{3/2}$ atomic transition. The $deltalangle r^{2}rangle^{A,221}$ values for $^{218m,219}text{Fr}$ and $^{229,231}text{Fr}$ follow the observed increasing slope of the charge radii beyond $N~=~126$. The charge radii odd-even staggering in this neutron-rich region is discussed, showing that $^{220}text{Fr}$ has a weakly inverted odd-even staggering while $^{228}text{Fr}$ has normal staggering. This suggests that both isotopes reside at the borders of a region of inverted staggering, which has been associated with reflection-asymmetric shapes. The $g(^{219}text{Fr}) = +0.69(1)$ value supports a $pi 1h_{9/2}$ shell model configuration for the ground state. The $g(^{229,231}text{Fr})$ values support the tentative $I^{pi}(^{229,231}text{Fr}) = (1/2^{+})$ spin, and point to a $pi s_{1/2}^{-1}$ intruder ground state configuration.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
