Underpopulated state

Now consider the kinetics of the flow of spins between spin states. For each pair of spin states, we calculate the difference in population and compare it to the equilibrium difference. If these two are not the same, there will be a flow of spins from the overpopulated state to the underpopulated state at a rate that is proportional to the rate constant for that transition and to the amount by which the transition is out of equilibrium. The rate constants, or relaxation rates, for each transition are determined by... 

Rotational Population Distributions. As expected, there is an overpopulation in the A state level and an underpopulation in the X state level connected by the laser, compared to a thermal distribution (see Fig. 1). Higher rotational levels (N 6) in the A-state are described by a Boltzmann distribution with T 940°K, well less than the gas temperature and reflecting the energy dependence of the or. The high-N levels of the X-state are described by a Boltzmann distribution with very high T (3200°K) but this may be an artifact of the model, due principally to the assumed... 

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