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Trim excess tape to minimize impurities. K shell. L shell. e- ~10 -18 s. g -ray. New precise a K measurement as a part of a test of internal conversion theory 166 keV transition in 139 La. Hole. x-ray. e- ~10 -17 s. Source A. Lanthanum K x-ray region. spectrum 1.

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slide1

Trim excess tape to minimize impurities

K shell

L shell

e-

~10-18 s

g-ray

New precise aK measurement as a part of a test of internal conversion theory166 keV transition in 139La

Hole

x-ray

e-

~10-17 s

Source A

Lanthanum K x-ray region

spectrum 1

spectrum 9, scaled

Impurities:

152Eum152Sm

152Eu  152Sm

152Eum  152Eu

Adhesive Mylar tape, 3.81 mm

Ba++(aq) + 2NO3-(aq)

Insulin

Mylar tape, 12.7 mm

g-ray

Ka

Kb

x-rays

Source A

Source B

7.0 mm

0.5 in

Source ready to be irradiated

Theoretical Calculations

Internal Conversion, Overview

  • Nuclear de-excitation energy transferred to an electron
    • Electron is emitted, followed by x-ray
    • Competes with g-ray emission
  • Internal Conversion Coefficient (ICC)
    • K-shell
    • I = intensityw = fluorescence yielde = detector efficiency
  • Impact
    • Nuclear decay schemes
      • Spin and parity assignments
      • Transition rates
      • Branching ratios
    • Detector calibration

139La Decay Scheme

C.M. Balonek, University at Buffalo

J.C. Hardy, N. Nica, Texas A&M University Cyclotron Institute

But Why?

  • Various ICC calculations disagree with one another and with experiment by several percent
  • Few ICC measurements have uncertainties under 1%
  • We will measure K-shell ICC values of three different transitions to better than 1% precision
    • ICCs for the 127.55 keV E3 transition from 134Csm and the661.657 keV M4 transition in 137Ba, have already been measured
    • 165.858 keV M1 transition in 139La is the third and final case

K X-Ray Analysis

  • Overlay of two spectra is used to identify impurities
  • Spectrum 1 (47 min) is largely 139La x-rays
  • Spectrum 9 (16 hr) contains x-rays from source impurities
  • Identified 3 different 152Eu transitions that contribute to this x-ray region

Spectral Analysis

  • Peaks identified according to energy and parent nuclei properties
  • 139Ba source produces strong peak at 166 keV
  • 139La K x-rays are another area of interest (29-42 keV)
    • Need to analyze impurities to accurately integrate this region

Source Preparation and Irradiation

Source Preparation

  • Ba(NO3)2(aq) placed on insulin-coated Mylar tape to produce micron-thick film of barium nitrate
    • Insulin aids in production of homogeneous film
  • Adhesive Mylar tape placed on film following solvent evaporation
  • Created two sources: A and B
  • Irradiated sources by neutron activation
    • Texas A&M Nuclear Science Center
  • Measured resulting x and g-rays
    • Germanium detector
      • Texas A&M University Cyclotron Institute
      • Relative photopeak efficiencies calibrated to 0.15%
    • 17 spectra recorded between ~1 and 24 hours after activation

Source A, spectrum 1 (47 min)

Preliminary Results

  • wK = K-shell fluorescence yield, 0.905(4)*
  • NK, Ng = total number of K x or g-rays found by integration of spectra
  • eK, eg = known detector efficiencies at energies of interest

*E. Schönfeld, H. Jaben, NIM A 369 (1996) 527.

A sincere thank you to Dr. John C. Hardy and Dr. Ninel Nica for their endless advisement throughout this project

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