Definition of nuclide re metastable states

[fsroberts]

The ground state of the isotope of Technetium that has a mass number of 99 is denoted by Tc-99. The metastable state is denoted by Tc-99m. Are these considered to be two different nuclides, or just two states of the same nuclide?
(I suspect that the definition of a nuclide takes into account not only mass number and atomic number, but energy state as well.)

For that matter, are they considered to be the same isotope or two different isotopes?

 

[marlon]

usually, a metastable state is a non-equilibrium state that can exist for a 'considerable' amount of time. it is indeed some state of one specific atom.

If you look at energy levels an excited atom has an electron from a lower level that has jumped to a higher level. now this is a non-equilibrium state because the atom will de-excite in order to lower the potential energy (nature is as lazy as possible). Now, in QM, you can prove that in some cases this electron does not go from high level A to low level B. When making the transition it can remain on an intermediate level C (A>C>B). Now if the electron remains in C longer then it has remained in A, then this C level corresponds to an intermediate metastable stage.

Something like that happens in lasers in order to obtain population inversion.

marlon

 

[fsroberts]

Exact definition of nuclide

The term 'metastability' is used in different contexts e.g. atomic energy levels, nuclear energy levels (which is what I am alluding to) and some electronic circuits.

I would just like to firm up on what is the precise definition of 'nuclide'? Is it sufficient to define a nuclide in terms of just its mass number and atomic number, or does one sometimes have to refer to energy states in the definition?

In other words, is the metastable {99m,27)Tc thought of as being the same nuclide as {99,27)Tc, or is it considered to be be a different nuclide because of its different energy state?

Basically, i am trying to get at the exact definition of a nuclide, because there seems to me to be an ambiguity in the definitions I've come across on the web.