# I Neutron Temperature

#### coolul007

Gold Member
Does temperature apply to subatomic particles, in particular the neutron? The question is prompted by the definition of absolute zero, being specific to atomic movement.

Related Other Physics Topics News on Phys.org

#### pangru

Does temperature apply to subatomic particles, in particular the neutron?
I am not sure if a get question properly but, in general, particles temperature can be defined with its kinetic energy
slow neutrons are colder, hot neutrons are faster..

as analogue of classical temperature, where $$T \sim <E_k>$$

#### ZapperZ

Staff Emeritus
2018 Award
Does temperature apply to subatomic particles, in particular the neutron? The question is prompted by the definition of absolute zero, being specific to atomic movement.
I don't think you understand the definition of temperature. It is a measure of the average kinetic energy of an ensemble of ANY particles, neutrons included.

If you do a search, you can even find, especially in a solid state text or webpage, the temperature of the "electron gas" in a conductor at room temperature.

Zz.

#### SpinFlop

Yes neutrons have a temperature. For non-relativistic free neutrons (eg: moderated neutrons radiating from a nuclear reactor) the equations are trivial $E = \frac{3}{2}k_{B}T$ where $E$ is the kinetic energy $E = \frac{1}{2}mv^{2}$. Indeed, at neutron scattering facilities dedicated to using neutrons as a probe of condensed matter, the different instruments are typically classified as cold, thermal, or hot. Which is a direct reference to the neutron temperatures used in the scattering experiments.

#### coolul007

Gold Member
I was thinking of temperature in the classic sense of atom versus subatomic particle. I have been lied to about atoms my whole life, so if I am way off base here I apologize. My understanding is the atoms increase "temperature" by absorbing photons. Therefore a rock that does not have kinetic energy can have "stored heat". Therefore, my thoughts went to particles that don't seem to absorb a photon and are at "rest" in the nucleus of an atom. That is what spurred my question.

#### BvU

Homework Helper
I have been lied to
That's a bit harsh. I probably got the same stories but don't share the feeling; learning is a gradual process that has to start somewhere. And what you can absorb in one step is limited (as well as what you can absorb in a whole lifetime ).

#### sophiecentaur

Gold Member
My understanding is the atoms increase "temperature" by absorbing photons.
I wouldn't say that is a meaningful statement. It's trying to extend a macroscopic, statistical idea into the behaviour of a single entity. Absorbing Energy doesn't imply a pro-rata increase in temperature, even in a real gas because input energy can result in an increase in Potential Energy as well as KE. Van der Vaal forces beween gas molecules stop them behaving ideally.
I would say that you haven't been "lied to" as much as taken an inappropriate message from a not-to-good presentation of the situation.

#### coolul007

Gold Member
That's a bit harsh. I probably got the same stories but don't share the feeling; learning is a gradual process that has to start somewhere. And what you can absorb in one step is limited (as well as what you can absorb in a whole lifetime ).
I didn't mean to be harsh, the implication is that, as understanding increases the previous teachings are invalidated. I'm 72 1/2 years old, so you can imagine the world, as well as the subatomic world has changed for me. I ask this question in relation to absolute zero, being the lack of "static" energy in an atom. I was just pondering if there is a subatomic equivalence. No condemnation of physicists on my part. Thank you for your replies.

BvU

#### StandardsGuy

I didn't mean to be harsh, the implication is that, as understanding increases the previous teachings are invalidated. I'm 72 1/2 years old, so you can imagine the world, as well as the subatomic world has changed for me. I ask this question in relation to absolute zero, being the lack of "static" energy in an atom. I was just pondering if there is a subatomic equivalence. No condemnation of physicists on my part. Thank you for your replies.
I think you're asking if neutrons have "internal" temperature as well as "external" temperature that SpinFlop described. Atoms can receive energy which pushes electrons into "higher orbits". I don't believe there is an equivalent in neutrons.

"Neutron Temperature"

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving