An absorption mode Lorentzian line, centred at frequency Ω is given by

We are going to work out the width of the line at half-height. Clearly, this is independent of the position of the line, so we can make the calculation simpler by assuming Ω = 0:

Show that the peak height is S0 and hence, by finding the values of ω (there are two) for which A(ω) = S0/(2R), show that the width of the line at half-height is 2R rads-1. Give the corresponding expression for the width in Hz.

SoR 4(a) =