New precise K measurement as a test of internal conversion theory

166 keV transition in 139La

Christine BalonekDr. John C. Hardy, AdvisorDr. Ninel Nica, Deputy AdvisorAugust 3, 2006

Overview

• Internal Conversion

• 139La Decay Scheme

• 139Ba Source

• Data Collection

• Spectral Analysis

• Impurity Analysis

• K X-Ray Analysis

• K Calculations

• Preliminary Results

• Summary

• Acknowledgements

• Nuclear de-excitation energy transferred to an electron– Electron is emitted and followed by an x-ray– In competition with -ray emission

• Internal Conversion Coefficient

–

• Impact– Nuclear decay schemes

• Spin and parity assignments

• Transition rates

• Branching ratios

– Detector calibration

e

Internal Conversion

x-ray

e-

~10-18 s

e-

~10-17 s

-ray

L shellL shell

K shellK shell

HoleHole

139La Decay SchemeLanthanum

K x-raysEnergy(keV) Intensity

1 33.442 46.8 11

2 33.034 25.7 6

1 37.801 8.7 19

2 38.726 2.81 6

3 37.72 4.51 10

139Ba Source

• Source design– Determine number of atoms

(mass of sample) required to produce desired -ray counts

• Preparation of sources– Obtain enriched barium

– Dilute Ba(NO3)2 in water

– Two sources, A and B

Adhesive Mylar tape, 3.81 m

Ba++(aq) + 2NO3

-(aq)

Insulin

Mylar tape, 12.7 m

Trim excess tape to minimize impurities

Source ready to be irradiated

7.0 mm0.5 in

• Layer Effects– Attenuation calculations

– Back scattering

Data collection

• Neutron irradiation of source– Texas A&M Nuclear Science Center

• and x-ray detection– Germanium detector, Cyclotron Institute,

Texas A&M University• Relative photopeak efficiencies calibrated

to 0.15%

– 17 spectra recorded between ~1 and 24 hours after activation

151. mm

and x-rays

Spectral Analysis

• Source A, Sept. 2005 irradiation, spectrum 1– 52.7 min elapsed time / 46.9 min live time (~0.6 half lives)

Impurity Analysis

K

K

-ray

x-rays

x-ray impurities

29.623 keV to 42.290 keV

-ray impurities

163.138 keV to 168.638 keV

K X-Ray AnalysisSpectrum 1, 0.88 hr

- largely 139La x-rays

Spectrum 9, 15.87 hr

- source impurity x-rays

K X-Ray Analysis

spectrum 9, scaledspectrum 1

Lanthanum K x-ray region

Impurities:152Eum 152Sm

152Eu 152Sm

152Eum 152Eu

153Sm 153Eu

K Calculation

• K-shell internal conversion coefficient, K

• K = K-shell fluorescence yield

– 0.905(4)*

• NK, N = total number of K x or -rays

– Integration of spectra after removal of impurities

• K, = detector efficiency for K x or -rays

– Known detector efficiencies at energies of interest

K

K

KK N

N

1

K

K

KK N

N

1

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

Preliminary Results

K

K

KK N

N

1

K

K

KK N

N

1

002.1

8387.0

3117232

770291

905.0

1K

002.1

8387.0

1752099

437196

905.0

1K

Source A, Sept. 2005 Irradiation Source B, July 2006 Irradiation

Theoretical Calculations

2231.0 K:hole With

2225.0 K:hole Without

27 2285.0K 28 2308.0K

Summary

• Successfully prepared and irradiated two enriched 139Ba sources

• Analyzed 17 spectra for impurities based on -ray energies and parent nuclei properties

• Performed quantitative x-ray analysis to subtract impurities

• Calculated preliminary values for K of 139La

• More detailed analysis of x-rays needed– Analysis is ongoing

• Next: 196Pt irradiation– K measurement for 197Au

Acknowledgements

• Dr. John C. Hardy, Advisor• Dr. Ninel Nica, Deputy Advisor• Hardy Research Group

– Victor Golovko, John Goodwin, Victor Iacob, Hyo In Park

• Texas A&M Cyclotron Institute REU Program– Dr. Sherry Yennello– Mary Ann Batson