What is the specific definition of N2* (with a superscript asterisk )? and its difference with some excited metastable species (e.g., N2(A3), N2(a')).
Is N2* just the joint name of all the N2 exicited metastable species?
But sometimes I saw N2* and N2(A3) were defined as two specific species, respectively.
The same question to H2*, H2(1s), or H*, H(1s) etc.
Thank you very much!
There is no general definition of N2*: Normally '*' is used to mark electronically excited states in general (for atoms, molecules, and electronically excited ionic species). Sometimes it is also used to mark a collection of specific excited states (i.e. for simplification of collisional-radiative modeling and simulation of plasmas). In such a case the energy degeneracy of this collection of excited states normally is defined as
g* = sum(g_i), where g_i is the degeneracy of a specific excited state,
and the energy is defined as
E* = sum(g_i x E_i)/g*, where E_i is the energy of a specific excited state. As you already suggested by your question, usually care is taken for not mixing short lived resonant states (states connected to the ground state by an optically allowed transition) with metastable states.
N2* is usually an excited nitrogen molecule, which is not ionised (so electrically neutral).
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