What is the role of kinetic energy in proton-proton fusion?

[Deepak247]

Ive studied how chain reaction of proton-proton powers the stars, I also know that proton-proton fusion will convert firstly one proton to neutron then fuse it with the other proton...my question is...

Is the main reason for them not being fused is that they both have +ve charge?

 

[mathman]

The fusion reaction is not quite as you described it. The input is 2 protons and the output is deuteron + positron + neutrino + energy. There is no intermediate step involving a proton becoming neutron + positron.

 

[kloptok]

The first nucleosynthesis taking place after Big Bang was p+n -> d + gamma, but in the proton-proton chain I think the first reaction is (contrary to what you are writing) p+p -> 2He + something (as is hinted by mathman in this thread).

 

[Deepak247]

Here is what i mean as the "FIRST STEP", forgive my English though:-

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/procyc.html#c1What I'm trying to say is what if somehow hypothetically i give a hypothetical charge 'X' to one proton, now would it fuse with the positive one?(such that the reason of proton-proton not fusing together is their +ve charge)

 

[mathman]

Here is what i mean as the "FIRST STEP", forgive my English though:-

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/procyc.html#c1


What I'm trying to say is what if somehow hypothetically i give a hypothetical charge 'X' to one proton, now would it fuse with the positive one?(such that the reason of proton-proton not fusing together is their +ve charge)

What is 'X'?? In that picture (first step) the two protons fuse into a deuteron plus other stuff.

 

[Deepak247]

What is 'X'?? In that picture (first step) the two protons fuse into a deuteron plus other stuff.

Yes, deuteron...of course, that's what i mean(forgive my english at beginning). Let 'X' be any other imaginary charge besides +ve, the point is "whether the reason of proton-proton not being fused is the +ve charge on both of them"...

 

[mathman]

Yes, deuteron...of course, that's what i mean(forgive my english at beginning). Let 'X' be any other imaginary charge besides +ve, the point is "whether the reason of proton-proton not being fused is the +ve charge on both of them"...

"Let 'X' be any other imaginary charge besides +ve"

I have no idea what you have in mind. In particular what is +ve? Also what do you mean by "imaginary charge"?

 

[Deepak247]

I have no idea what you have in mind. In particular what is +ve? Also what do you mean by "imaginary charge"?

Ok...lets make it real simple,

In proton-proton chain reaction, do the two protons do not fuse because of their positive charge? is that the reason a proton and a neutron fuses because of different charge?
Yes or No?

 

[mathman]

Ok...lets make it real simple,

In proton-proton chain reaction, do the two protons do not fuse because of their positive charge? is that the reason a proton and a neutron fuses because of different charge?
Yes or No?

The protons do fuse and the result is as described. I can only repeat the proton does not become a neutron before the reaction - only as part of the process.

 

[Deepak247]

The protons do fuse and the result is as described. I can only repeat the proton does not become a neutron before the reaction - only as part of the process.

Thanks for the reply but you forgot to mention about the positive charge prospect i mentioned, Please Please if possible (In yes or no will also do)...

 

[Astronuc]

Ok...lets make it real simple,

In proton-proton chain reaction, do the two protons do not fuse because of their positive charge? is that the reason a proton and a neutron fuses because of different charge?
Yes or No?

No, a proton and neutron may readily combine to become a deuteron. The reaction is called 'neutron capture', and it is rather common, and in the process, a gamma ray is emitted.

Deutrons can also experience photodisintegration, a process in which a gamma ray of some energy greater than some threshold, ~2.2 MeV, can cause the deuteron to dissociate into a neutron and proton.

Two protons fuse, but they must have enough kinetic energy to approach each other closely enough to fuse. More often though, they scatter without fusing - otherwise stars would consume hydrogen very rapidly.

See - http://hyperphysics.phy-astr.gsu.edu/hbase/astro/procyc.html
http://hyperphysics.phy-astr.gsu.edu/hbase/astro/solarpp.html

http://csep10.phys.utk.edu/astr162/lect/energy/ppchain.html

 

[Deepak247]

Two protons fuse, but they must have enough kinetic energy to approach each other closely enough to fuse. More often though, they scatter without fusing - otherwise stars would consume hydrogen very rapidly.

Thank you very much for your reply Astronuc...It helped me a lot...
However It made me bother to ask a few more questions(just for the sake of one's knowledge)...Your reply is eagerly awaited...

Q1) How much more "kinetic energy" is needed for p-p to fuse? (I've heard somewhere that if Strong force was 2% more strong they would fuse), but what about the kinetic energy?

Q2) I want to learn more on this "Kinetic Energy" factor which makes fusion between nuclei possible, Is Schrödinger equation (for wave function) the right start ?