scholarly journals Clustering in $^{18}$O - absolute determination of branching ratios via high-resolution particle spectroscopy

2020 ◽  
Author(s):  
Stuart Pirrie ◽  
Carl Wheldon ◽  
Tzany Kokalova ◽  
Jack Bishop ◽  
R. Hertenberger ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Excited State ◽  
High Resolution ◽  
Cluster Structure ◽  
High Energy ◽  
Branching Ratios ◽  
Light Nuclei ◽  
Decay Channels ◽  
Monte Carlo Techniques

The determination of absolute branching ratios for high-energy states in light nuclei is an important and useful tool for probing the underlying nuclear structure of individual resonances: for example, in establishing the tendency of an excited state towards \alphaα-cluster structure. Difficulty arises in measuring these branching ratios due to similarities in available decay channels, such as (\mathbf{^{18}}18O,\mathbf{n}𝐧) and (\mathbf{^{18}}18O,\mathbf{2n}2𝐧), as well as differences in geometric efficiencies due to population of bound excited levels in daughter nuclei. Methods are presented using Monte Carlo techniques to overcome these issues.

scholarly journals Precision branching-ratio measurements in $$^{18}$$O

2021 ◽  
Vol 57 (4) ◽  
Author(s):  
S. Pirrie ◽  
C. Wheldon ◽  
Tz. Kokalova ◽  
J. Bishop ◽  
Th. Faestermann ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Branching Ratio ◽  
High Energy ◽  
Branching Ratios ◽  
Monte Carlo Techniques ◽  
Energy States

AbstractAn experiment has been performed utilising the $$^{12}$$ 12 C($$^{7}$$ 7 Li,p)$$^{18}$$ 18 O reaction to populate high-energy states in $$^{18}$$ 18 O. Using the Munich Q3D magnetic spectrograph in conjunction with the Birmingham large-angular-coverage DSSD array, branching ratios have been measured for over fifty states in $$^{18}$$ 18 O, investigating the $$\alpha $$ α -decay, n-decay, 2n-decay and $$\gamma $$ γ -decay branches. In tandem, Monte-Carlo techniques have been used to identify and separate features.

Neutron dose evaluation of Elekta Linac at two energies (10 & 18 MV) by MCNP code and comparison with experimental measurements

2014 ◽  
Vol 6 (1) ◽  
pp. 1006-1015
Author(s):  
Negin Shagholi ◽  
Hassan Ali ◽  
Mahdi Sadeghi ◽  
Arjang Shahvar ◽  
Hoda Darestani ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Measurement Data ◽  
Calculated Data ◽  
High Energy ◽  
Neutron Dose ◽  
Dose Assessment ◽  
Photon Flux ◽  
Dose Equivalent ◽  
Monte Carlo Techniques ◽  
Neutron Dose Equivalent

Medical linear accelerators, besides the clinically high energy electron and photon beams, produce other secondary particles such as neutrons which escalate the delivered dose. In this study the neutron dose at 10 and 18MV Elekta linac was obtained by using TLD600 and TLD700 as well as Monte Carlo simulation. For neutron dose assessment in 2020 cm2 field, TLDs were calibrated at first. Gamma calibration was performed with 10 and 18 MV linac and neutron calibration was done with 241Am-Be neutron source. For simulation, MCNPX code was used then calculated neutron dose equivalent was compared with measurement data. Neutron dose equivalent at 18 MV was measured by using TLDs on the phantom surface and depths of 1, 2, 3.3, 4, 5 and 6 cm. Neutron dose at depths of less than 3.3cm was zero and maximized at the depth of 4 cm (44.39 mSvGy-1), whereas calculation resulted  in the maximum of 2.32 mSvGy-1 at the same depth. Neutron dose at 10 MV was measured by using TLDs on the phantom surface and depths of 1, 2, 2.5, 3.3, 4 and 5 cm. No photoneutron dose was observed at depths of less than 3.3cm and the maximum was at 4cm equal to 5.44mSvGy-1, however, the calculated data showed the maximum of 0.077mSvGy-1 at the same depth. The comparison between measured photo neutron dose and calculated data along the beam axis in different depths, shows that the measurement data were much more than the calculated data, so it seems that TLD600 and TLD700 pairs are not suitable dosimeters for neutron dosimetry in linac central axis due to high photon flux, whereas MCNPX Monte Carlo techniques still remain a valuable tool for photonuclear dose studies.

A Pulsed Photoacoustic Microcalorimeter for the Detection of Upper Excited-State Processes and Intersystem Crossing Yields

1989 ◽  
Vol 43 (5) ◽  
pp. 826-833 ◽  
Author(s):  
Daniel Lynch ◽  
John F. Endicott
Keyword(s):  
Excited State ◽  
Excited States ◽  
Excellent Agreement ◽  
Piezoelectric Transducer ◽  
Detection System ◽  
High Energy ◽  
Intersystem Crossing ◽  
Photoacoustic Detection ◽  
Deconvolution Techniques

A photoacoustic detection system is described that has excellent linearity and limits of detection, and which is simple to implement. This system has been applied to the determination of intersystem crossing yields, φisc, of a series of Cr(NN)33+ complexes. The results are in excellent agreement with the literature values for two of these complexes. Results for two other complexes determined that there are long-lived (τ < 15 ns) upper excited states or other high-energy species produced that prevent rapid relaxation to the lowest energy excited state of these complexes. Without the need to resort to deconvolution techniques, this method can be used on systems that have rapid relaxation (τ < 1 ns) of the upper excited states and lifetimes <5 μs for the lowest energy excited state, with the application of a 5 MHz piezoelectric transducer.

High-Resolution Vibrational Spectra of Furazan IV. The Aj Fundamental v2 at ~ 1418 cm-1 from Fourier-Transform Infrared Spectroscopy

1993 ◽  
Vol 48 (5-6) ◽  
pp. 692-698
Author(s):  
Otto L. Stiefvater ◽  
Stefan Klee
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Excited State ◽  
High Resolution ◽  
Band Origin ◽  
Asymmetric Rotor ◽  
Stretching Vibration ◽  
Ft Ir ◽  
Microwave Data

Abstract The band origin of the A1 mode v2 , which represents the symmetrical stretching vibration of the two C = N bonds of furazan, has been determined from the high-resolution FT-IR band as v20 = 1418.4724± 0.0001 cm-1. The rotational parameters of this excited state, as determined in a preceding DRM microwave study, have been confirmed and their precision was raised through the combined fit of microwave data and of some 2500 rovibrational transitions.The use of conjugate low-J Q-branch lines for the determination of the origin of a B-type IR band of an asymmetric rotor is illustrated.

scholarly journals Devitrification reduces beam-induced movement in cryo-EM

IUCrJ ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 186-194
Author(s):  
Jan-Philip Wieferig ◽  
Deryck J. Mills ◽  
Werner Kühlbrandt
Keyword(s):  
High Resolution ◽  
Structure Determination ◽  
High Energy ◽  
Full Potential ◽  
High Energy Electrons ◽  
High Resolution Structure ◽  
Image Blurring ◽  
Particle Images ◽  
Resolution Structure

As cryo-EM approaches the physical resolution limits imposed by electron optics and radiation damage, it becomes increasingly urgent to address the issues that impede high-resolution structure determination of biological specimens. One of the persistent problems has been beam-induced movement, which occurs when the specimen is irradiated with high-energy electrons. Beam-induced movement results in image blurring and loss of high-resolution information. It is particularly severe for biological samples in unsupported thin films of vitreous water. By controlled devitrification of conventionally plunge-frozen samples, the suspended film of vitrified water was converted into cubic ice, a polycrystalline, mechanically stable solid. It is shown that compared with vitrified samples, devitrification reduces beam-induced movement in the first 5 e Å−2 of an exposure by a factor of ∼4, substantially enhancing the contribution of the initial, minimally damaged frames to a structure. A 3D apoferritin map reconstructed from the first frames of 20 000 particle images of devitrified samples resolved undamaged side chains. Devitrification of frozen-hydrated specimens helps to overcome beam-induced specimen motion in single-particle cryo-EM, as a further step towards realizing the full potential of cryo-EM for high-resolution structure determination.

Laboratory plasmas for high-energy astrophysics: A method to measure effective Landé g-factors

2019 ◽  
Vol 15 (S350) ◽  
pp. 326-329
Author(s):  
Marina Giarrusso
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Cyclotron Resonance ◽  
Electron Cyclotron Resonance ◽  
High Energy ◽  
High Energy Astrophysics ◽  
Angular Momenta ◽  
Laboratory Plasmas ◽  
The One

AbstractEffective Landé g-factors (geff) are fundamental quantities in order to derive stellar magnetic field intensities. The determination of geff involves both total angular momenta and Landé g-factors of the transition levels. Theoretical g-factors are generally adopted, and the corresponding geff, often quite different from the one obtained in laboratory, affects the accuracy on magnetic field strength measurements. In this work we discuss a method to experimentally determine geff for highly ionised species, based on high resolution spectropolarimetry applied to Electron Cyclotron Resonance laboratory plasmas.

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