= (4/3ħc) n em2 (Nm-Nn) (o-) 1 2 3 4 Square of the transition moment n em2 Frequency of the light Population difference (Nm- Nn) Resonance factor - Dirac delta function (0) = 1
= (4/3ħc) n em2 (Nm-Nn) (o-) 1 2 3 4 (Nm- Nn)
I = Ioe-γl Beer’s Law
I = Ioe-γl
I = Ioe-γl = (4/3ħc) n em2 (Nm-Nn) (o-) 1 2 3 4 1 2 3 4 Three Cases
I = Ioe-γl = (4/3ħc) n em2 (Nm-Nn) (o-) 1 2 3 4 1 2 3 4 Three Cases Nm > Nn
I = Ioe-γl = (4/3ħc) n em2 (Nm-Nn) (o-) 1 2 3 4 1 2 3 4 Three Cases Nm > Nn +ve
I = Ioe-γl = (4/3ħc) n em2 (Nm-Nn) (o-) 1 2 3 4 1 2 3 4 Three Cases Nm > Nn +ve I < Io Absorption
I = Ioe-γl = (4/3ħc) n em2 (Nm-Nn) (o-) 1 2 3 4 1 2 3 4 Three Cases Nm > Nn +ve I < Io Absorption Nm = Nn
I = Ioe-γl = (4/3ħc) n em2 (Nm-Nn) (o-) 1 2 3 4 1 2 3 4 Three Cases Nm > Nn +ve I < Io Absorption Nm = Nn = 0
I = Ioe-γl = (4/3ħc) n em2 (Nm-Nn) (o-) 1 2 3 4 1 2 3 4 Three Cases Nm > Nn +ve I < Io Absorption Nm = Nn = 0 I = Io Saturation
I = Ioe-γl = (4/3ħc) n em2 (Nm-Nn) (o-) 1 2 3 4 1 2 3 4 Three Cases Nm > Nn +ve I < Io Absorption Nm = Nn = 0 I = Io Saturation Nm < Nn
I = Ioe-γl = (4/3ħc) n em2 (Nm-Nn) (o-) 1 2 3 4 1 2 3 4 Three Cases Nm > Nn +ve I < Io Absorption Nm = Nn = 0 I = Io Saturation Nm < Nn -ve
I = Ioe-γl = (4/3ħc) n em2 (Nm-Nn) (o-) 1 2 3 4 1 2 3 4 Three Cases Nm > Nn +ve I < Io Absorption Nm = Nn = 0 I = Io Saturation Nm < Nn -ve I > Io Stimulated Emission
The maser may switch of after say 3 days so the dimension of the cloud can be estimated from the time for the light wave to pass through the cloud as about 1/100th of a ly and leave the molecules in their lower states. It will take several days to pump up to population inversion again and switch on again Harry Kroto 2004