Update of Internal Conversion Coefficient Measurement: 150.8-keV, E3 transition in 111m Cd TEXAS...

Update of Internal Conversion Coefficient Measurement:

150.8-keV, E3 transition in 111mCd TEXAS A&M PROGRAM TO MEASURE ICC

N. NICA

Internal Conversion Coefficients (ICC):

• Big impact on quality of nuclear science

• Central for NSDD and other nuclear data programs

• Intensely studied by theory and experiment

• Important result: hole calculation now standard

2002RA45 survey ICC’s theories and measurements• Theory: RHFS and RDF comparison Exchange interaction, Finite size of nucleus, Hole treatment• Experiment:

100 E2, M3, E3, M4, E5 ICC values, 0.5%-6% precision, very few <1% precision!

• Conclusions, Δ(exp:theory)%: No hole: +0.19(26)% BEST! (bound and continuum states - SCF of neutral atom)

Hole-SCF: -0.94(24)% (continuum - SCF of ion + hole (full relaxation of ion orbitals))

Hole-FO: -1.18(24)% (continuum - ion field from bound wave functions of neutral atom (no relaxation of ion orbitals))

PHYSICAL ARGUMENTK-shell filling time vs. time to leave atom

~10-15 – 10-17 s » ~10-18 s

2002Ra45: 100 αK(exp) cases compared with ‘hole FO’ calculations

Overview of the scope and completeness of the method

There is no criterion to reach the scope of comparison between ICC theories “with hole” and “no hole” except for measuring precisely as many relevant cases as practically

possible

The difference ΔK between αK(‘hole’) and αK(‘no hole’) (relative to αK(‘hole’)) as function of kinetic energy of converted electron EK

Overview of the scope and completeness of the method

Is the series of measurements complete?1. Re-measure ‘main set’ of 100 cases

2. Measure other cases

3. Abnormal results

4. High uncertainties

5. Experiment: about 1-2% precision

6. Theory: ΔK = 7-10%, ΔK = 4-7%

7. Well spread on nuclear chart

111mCd 150.8 keV, E3 transition

Suggested by 1984Ba84

α(K)exp = 1.29 11 (1987Ne05), %unc=8.5

α(K)hole_FO = 1.450, α(K)no_hole = 1.425, ΔK = 1.7%

Texas A&M precision ICC measurements:

KX to γ rays ratio method

K

KKK N

N

o NK, Nγ measured from only one K-shell converted transition

o ωK from 1999SCZX (compilation and fit)

Very precise detection efficiency for ORTEC -X 280-cm3 coaxial HPGe at standard distance of 151 mm:

0.2% , 50-1400 keV (2002HA61, 2003HE28)

0.4% , 1.4-3.5 MeV (2004HE34)

1% , 10-50 keV (KX rays domain)

KX to γ rays ratio method

o Sources for nth activation Small selfabsorption (< 0.1%) Dead time (< 5%) Statistics (> 106 for γ or x-rays) High spectrum purity Minimize activation time (0.5 h)

o Impurity analysis - essentially based on ENSDF Trace and correct impurity to 0.01% level Use decay-curve analysis Especially important for the K X-ray region

o Voigt-shape (Lorentzian) correction for X-rays

Done by simulation spectra, analyzed as the real spectra

o Coincidence summing correction

111mCd 150.8 keV, E3 transition - K measurement

110Cd 95.88% enriched (from 12.5% natural abundance), thin metal powder from Trace Sciences International.

Impurities: 106Cd (<0.01%), 108Cd (<0.02%), 114Cd (0.84%), 116Cd (<0.16%).

Backing: 10 µm Al foil (99.999%) from GoodFellow. Samples prepared by electro deposition by Dr. C. Folden III

and Drd. T. Werke Samples: CdO, Φ=1.7 cm on 10 µm Al backing

S1: 0.99(2) mg, 0.53(1) µm S2: 1.08(2) mg, 0.58(1) µm

Neutron activation at Triga reactor @ TAMU, on both S1 and S2: = 7.5 x 1012 n/(cm2s) σth = 0.14(5) b Samples activated 2 h, then cooled down for 2 hours Measured for 3 weeks

109Cd Efficiency Calibration 22.6-keV AgKx & 88.0-keV E3 γ regions

111mCd 150.5 keV, E3 transition - K measurementImpurity analysis

S2, sp. 1

Impurity Contribution to Cd KX rays111mCd 11.24% 0.21%115Cd 2.26% 0.08%117Cd 0.113% 0.012%117In 0.21% 0.03%117mIn 0.467% 0.009%116mIn 0.0063% 0.0011%

Total 14.30% 0.22%

S2, sp. 2

Impurity Contribution to Cd KX rays111mCd 11.20% 0.20%115Cd 3.12% 0.07%117Cd 0.145% 0.010%117In 0.24% 0.03%117mIn 0.559% 0.006%116mIn 0.0069% 0.0011%

Total 15.27% 0.22%

S2, sp. 3

Impurity Contribution to Cd KX rays111mCd 11.10% 0.20%115Cd 5.57% 0.11%117Cd 0.188% 0.012%117In 0.39% 0.05%117mIn 0.873% 0.007%116mIn 0.0045% 0.0012%

Total 18.12% 0.24%

S1, sp. 1

Impurity Contribution to Cd KX rays111mCd 11.26% 0.21%115Cd 2.07% 0.08%117Cd 0.130% 0.014%117In 0.21% 0.03%117mIn 0.689% 0.010%116mIn 0.0124% 0.0020%

Total 14.37% 0.22%

αK(150.8)

α(150.8)

S2, sp.1 1.452 0.015 1.06% 2.251 0.029 1.30% S2, sp.2 1.451 0.014 0.99% 2.236 0.027 1.22% S2, sp.3 1.462 0.013 0.91% 2.233 0.024 1.07% S1, sp.1 1.449 0.016 1.08% 2.250 0.030 1.33%

αK(150.8)

α(150.8) Exp(W.Aver) 1.454 0.007 0.50% 2.241 0.014 0.61%

Theor(FO) 1.450

2.28 Theor(NH) 1.425

2.26

1987Ne05 1.29 0.11 8.53% 1.98 0.05 2.53%

111mCd 150.5 keV, E3 transition -

K measurement

Preliminary results