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Topic: neutron  (Read 9310 times)

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Offline khwcm

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neutron
« on: March 17, 2010, 11:07:17 AM »
Chadwick, the chemist who discovered the neutron, use the following method to produce neutron:
Alpha particle hit to a thin sheet of beryllium, a neutron will be given off.
i wonder that: the neutron came from beryllium or alpha particle, and why?

Offline gippgig

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Re: neutron
« Reply #1 on: March 17, 2010, 09:22:16 PM »
When 4He (an alpha particle) hits (with sufficient energy) 9Be it can form an excited state of 13C, which deexcites by emitting a neutron. The compound nucleus is formed before the neutron is emitted so the source of the neutron is the compound nucleus, not either of the starting nuclei.

Offline khwcm

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Re: neutron
« Reply #2 on: March 19, 2010, 07:39:35 AM »
since 9Be + 4He --> 13C
so do u mean that when C-13 deexcited, it is possible that the neutrons given out were came from alpha particles?(because there are 2 neutron from He-4 in C-13)

Offline Borek

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Re: neutron
« Reply #3 on: March 19, 2010, 09:13:49 AM »
Neutrons are indistinguishable.
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Offline khwcm

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Re: neutron
« Reply #4 on: March 19, 2010, 09:35:03 AM »
i am not asking for the prove =.='''
i am just asking: is it POSSIBLE to be a neutron from alpha particle.
(just like probability, ie: electronic diagram -- we cannot see the s orbital/distinguish a particular electron at particular place, but we may have may found the electron with 90% in it)

Offline sjb

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Re: neutron
« Reply #5 on: March 19, 2010, 11:46:17 AM »
As Borek has said, for the minute neutrons are indistinguishable. As there are 7 neutrons in 13C, and 2 have come from the alpha particle, I guess Occam's razor would suggest that there is 2/7 chance the ejected neutron has come from the alpha particle.

Offline khwcm

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Re: neutron
« Reply #6 on: March 19, 2010, 01:05:19 PM »
thanks....i finally got the answer...
btw....the prob should be 2/13 rather than 2/7, isnt it?

Offline sjb

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Re: neutron
« Reply #7 on: March 19, 2010, 01:46:17 PM »
Why do you think it is 2/13?

Offline Borek

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Re: neutron
« Reply #8 on: March 19, 2010, 01:53:33 PM »
What does 13 in 13C mean?
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Offline khwcm

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Re: neutron
« Reply #9 on: March 20, 2010, 03:43:14 AM »
ar...i think i got it !..thanks

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