[yor_on (OP)]

Saw someone write

" The subatomic particles that make up the nuclei of atoms can be broken apart by giving them sufficient kinetic energy, but this usually occurs by single collisions with other subatomic particles (which is an orderly addition of kinetic energy in a single collision with a single other particle), rather than by adding heat (which is a chaotic addition of kinetic energy over the course of many randomised collisions with other particles). "

Which, if I read it right, would make a laser unable to 'heat' a isolated atom, 'shooting' photons at it in a orderly manner?

[alancalverd]

It would work OK if the laser could deliver more than about 1 MeV  photons. Not sure what the lowest threshold is, but photonuclear disintegration is observed.

Heat is a collective property: temperature is the mean kinetic energy of a bounded set of particles, and heat is the total ke of that group within that boundary. A single atom whizzing through space at 0.999c has plenty of energy but no temperature.

[yor_on (OP)]

Thanks Alan :)

[Bored chemist]

Which, if I read it right, would make a laser unable to 'heat' a isolated atom, 'shooting' photons at it in a orderly manner?

"Heat" isn't well defined for an isolated atom.

[yor_on (OP)]

Could you expand on that BC?

[Bored chemist]

Could you expand on that BC?

Credit where it's due:
Alan summed it up.

Heat is a collective property: temperature is the mean kinetic energy of a bounded set of particles, and heat is the total ke of that group within that boundary. A single atom whizzing through space at 0.999c has plenty of energy but no temperature.

[yor_on (OP)]

No interactions so no heat. How about radiation? So it shouldn't radiate, right?

How about a wave packet, a 'photon'.

https://faculty.washington.edu/seattle/physics541/2012-reading/photon2.pdf

[alancalverd]

Photons are radiated when a charged particle accelerates or changes quantum state.
A photon is not a charged particle.