Superradiating 4P-4S-3P cascade of sodium vapour arising on the leading edge of the exciting laser pulse

Investigations of the superradiating cascade of sodium vapour 4P-4S-3P₁ = 2.21 µm and₂=1.14 µm) arising on the leading edge of the exciting laser pulse were carried out. The dependences of the actual delay time_D of the₁ pulse on the population rise time of the laser-excited 4P state were measured and compared with those calculated following the existing theoretical model. The dependence of the actual delay time_D on the inverse density of excited atoms 1/N* is also presented. Analysis of this dependence revealed the influence of the Doppler dephasing and of the second,₂, transition on the formation of the₁ superradiance.