Natural Radioactivity of Lanthanum and Neodymium [Thesis]

Thesis/Dissertation · Sat May 31 00:00:00 EDT 1952

OSTI ID:4379969

Mulholland, George I. ^[1]

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1. Carnegie Inst. of Technology, Pittsburgh, PA (United States)

A search was made for natural activity of neodymium and lanthanum using a proportional counter of large surface area and 50% geometry. The background was reduced by means of massive shielding and guard counters connected in anticoincidence. Normal analytical and radiochemical techniques and repeated ion exchange column separations were used to obtain pure samples. Ten grams of lanthanum oxide gave a counting rate of 54.0 ± 0.6 counts per minute when spread over an area of 1650 cm². Analysis of an aluminum absorption curve yielded a specific activity for beta radiation of 0.07 disintegrations per second per gram of lanthanum and a partial half-life of 1.2 X 10¹² years for La¹³⁸. The maximum energy of the beta particles, believed to be negative, is estimated to be 1.0 ± 0.2 Mev. The x-radiation associated with electron-capture decay to Ba¹³⁸ was also measured. This gave a specific activity of 1.0 x-rays per second per gram of lanthanum, corresponding to an electron-capture specific activity of 1.2 disintegrations per second per gram of lanthanum and an electron-capture partial half-life of 7 X 10¹⁰ years for La¹³⁸. The net half-life is essentially that of electron capture. The log₁₀ft for the negatron transition is 21.3, which seems consistent with a fourth-forbidden transition from $$_{57}\text{La}^{138}_{81}$$ in a $$\text{g}_{7/2^{-d}3/2}$$ configuration with spin 5 and even parity. At most 1 count per minute of soft or hard radiation was observed from 15 grams of neodymium oxide spread over an area of 1650 cm², whereas from the results of Libby (1934) about 270 counts per minute would be expected. The maximum specific hard beta activity is 0.003 disintegrations per second per gram of neodymium, corresponding to a minimum halflife of 2 X 10¹⁵ years for Nd¹⁵⁰. Reasons are given for supposing Nd¹⁵⁰ to be unstable but with a very long half-life. The maximum specific alpha activity is 0.02 disintegrations per second per gram of neodymium.

• Research Organization: Carnegie Inst. of Technology, Pittsburgh, PA (United States)
• Sponsoring Organization: US Atomic Energy Commission (AEC)
• NSA Number: NSA-06-006720
• OSTI ID: 4379969
• Report Number(s): NYO--3228
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALPHA DECAY
BACKGROUND
BARIUM 138
BETA DECAY
COINCIDENCE METHODS
ENERGY LEVELS
ENERGY RANGE
GAMMA RADIATION
HALF-LIFE
INTERNAL CONVERSION
ION EXCHANGE
LANTHANUM
LANTHANUM 138
LANTHANUM OXIDES
MEASURED VALUES
NEODYMIUM
NEODYMIUM 150
PARITY
PROPORTIONAL COUNTERS
RADIOACTIVITY
SPIN