The fusion process that powers the sun and other stars primarily involves the conversion of hydrogen into helium through a series of reactions. Let's outline the major steps in one of the simplest fusion cycles known as the proton-proton chain reaction (P-P chain):
1. First Step: Two protons ([tex]\( {}_1^1H \)[/tex]) collide and fuse to form a deuterium nucleus ([tex]\( {}_1^2H \)[/tex]), a positron ([tex]\( e^+ \)[/tex]), and a neutrino ([tex]\( \nu \)[/tex]):
[tex]\[
{}_1^1H + {}_1^1H \rightarrow {}_1^2H + e^+ + \nu + \text{energy}
\][/tex]
2. Second Step: A deuterium nucleus ([tex]\( {}_1^2H \)[/tex]) collides with a proton ([tex]\( {}_1^1H \)[/tex]) to produce a helium-3 nucleus ([tex]\( {}_2^3He \)[/tex]) and releases energy:
[tex]\[
{}_1^2H + {}_1^1H \rightarrow {}_2^3He + \text{energy}
\][/tex]
3. Third Step: Two helium-3 nuclei ([tex]\( {}_2^3He \)[/tex]) collide and fuse to form a helium-4 nucleus ([tex]\( {}_2^4He \)[/tex]) and two protons ([tex]\( {}_1^1H \)[/tex]), releasing energy:
[tex]\[
{}_2^3He + {}_2^3He \rightarrow {}_2^4He + 2 {}_1^1H + \text{energy}
\][/tex]
Now, examining the provided options for the full fusion process, we can see that the second step corresponds to:
[tex]\[
{}_1^2H + {}_1^1H \rightarrow {}_2^3He + \text{energy}
\][/tex]
This is the second reaction in the proton-proton chain fusion process.
