Question

Define transition probability and einstein cofficients

Answer 1

transition probability means:

the probability of the occurrence of a transition between two quantum states of an atom, nucleus, electron, etc.

Einstein coefficients:

Einstein coefficients are mathematical quantities which are a measure of the probability of absorption or emission of light by an atom or molecule.

Answer 2

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We give the following definitions. Definitions: A thermodynamic phase of a simple material is an open, connected region in the space of thermodynamic states parametrized by the variables T and µ, the pressure P being analytic in T and µ. ... Phase transitions occur on crossing a phase boundary.