Ground-state rotational temperature measurement, electronic

One is familiar with the idea of discrete and definite electronic stales in molecules, as revealed by molecular spectroscopy. Each electronic stale possesses a number of vibrational states that are occupied to a great extent near the ground state at normal temperatures. Each vibrational state has, if the stcric conditions are enabling, a number of rotational states associated with it, and for gas molecules both the vibrational and the rotational states can easily be observed and measured spectroscopically. Correspondingly, the distribution of the vibrational states in solids (phonon spectra) is easily measurable. 

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