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Q49E

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Modern Physics
Found in: Page 520
Modern Physics

Modern Physics

Book edition 2nd Edition
Author(s) Randy Harris
Pages 633 pages
ISBN 9780805303087

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Short Answer

What is the recoil speed of the daughter nucleus when 67152Ho α decays.

The recoil nucleus's speed is 3.94×105 m/s.

See the step by step solution

Step by Step Solution

Step 1: Given data

The Given Element is 67152Ho.

Step 2: Concept of Energy released during Electron Capture

During electron capture, the amount of energy released depends on the mass difference between the parent and the daughter nucleus.

Which is:

Q=(mparent mdaughter )c2 .

Where mparent is the atomic mass of the parent nucleus, and mdaughter is the atomic mass daughter nucleus.

Step 3: Determine the Recoil Speed from the energy released during Electron Capture

The alpha decay of 67152Ho is:

67152Ho24α+65148 Tb

The Q factor can be calculated as:

Q=(mparent mdaughter )c2=(151.931580u4.002603u147.924140u)×(931.5 MeV/u)=4.51 MeV

Assume the speed of the recoil nucleus is vTb then from momentum conservation, we have:

mTbvTb+mαvα=0

Rearrange the above equation for vα as:

vα=mTbvTbmα

The total kinetic energy is given by the Q factor, so we obtain:

Q=KETb+KEa=12mTbvTb2+12mαvα2=12vTb2mTb+mTb2ma

Rearrange the above equation for vTb as:

vTb=2QmTb+mTb2mα

Substitute values in the above equation, the recoil speed of the daughter nucleus is given below as:

vTb=2QmTb+mTb2ma=2(4.51 MeV)(147.924140u)+(147.922140u)24.002603u=(9.02 MeV)(5614.75u) c2931.5 MeV/u=1.313×103c

Calculate further as:

vTb=1.313×103c=1.313×103(3.0×108  m/s)=3.94×105  m/s

The recoil nucleus's speed is 3.94×105  m/s .

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