= Boltzmann’s constant, =
.
= the ionization potential.
This is the number of atoms which is effective in absorbing the ultimate lines at that temperature. For low values of
, the number of unionized atoms falls off at first very slowly with rising temperature, up to a point depending only on the ionization potential. Beyond this temperature the number of neutral atoms falls off with great rapidity. The diagram ([Figure 5]) illustrates the fall in the number of neutral atoms, and the consequent decay in strength of the ultimate lines. So steep is the gradient of
