[thedoc (OP)]

Aman Sharma  asked the Naked Scientists:
   
Hello! Chris

What happens when hydrogen atoms collide in high pressure conditions. What are the resultant subatomic particles after collision?

Aman Sharma

What do you think?

[evan_au]

Under high-pressure conditions (eg the center of Jupiter), it is thought that hydrogen atoms will turn into a metal, which may be a superconductor. There is some progress towards demonstrating this in the laboratory: http://en.wikipedia.org/wiki/Metallic_hydrogen

Under more normal-pressure conditions (or even low-pressure conditions), two colliding hydrogen atoms will form a covalent bond, to make hydrogen gas, H₂.

Under higher-energy conditions, the H₂ gas will immediately break up again into individual Hydrogen atoms.

Even higher-energy conditions (like the surface of the Sun) will even rip the electrons off the nuclei, to make a plasma.

Under extremely high-energy conditions and high pressures (like the center of the Sun), the electrostatic repulsion of the nuclei may be overcome; they will mostly bounce off again, but they sometimes fuse together to make deuterium+positron+neutrino: http://en.wikipedia.org/wiki/Proton%E2%80%93proton_chain_reaction#The_proton.E2.80.93proton_chain_reaction

Under extraordinarily high energy conditions (like the LHC), colliding hydrogen nuclei can make almost any particle which has an energy less than one colliding nucleus (including some that might be like a Higgs Boson).
A video showing the quarks inside a hydrogen nuclei colliding is shown here:

The LHC is trying to probe the types of events that may have happened soon after the Big Bang, as shown here:
http://www.youtube.com/watch?NR=1&feature=endscreen&v=io8rQrQUxEc