Experimental verification of the relation between the delay time and the tipping angle for a superradiant pulse

According to Dicke's theory of superradiance, the relation between the delay time t(0) and the tipping angle delta(0) for superradiant pulses can be expressed by t(0) = -tau(R) ln[tan(delta(0)/2)], where tau(R) is the radiation damping time constant. This relation is verified by nuclear magnetic resonance (NMR) experiments on a normal water sample. The radiation damping time t(R) and the delay time t(0) are independently measured, and the tipping angle delta(0) is evaluated. The tipping angle can be as big as several degrees if the spin inversion is not perfect. It can also be as small as 10(-8) rad, when the residual coherence in the transverse plane is destroyed by a strong field gradient pulse.