We present a kinetic study of the reaction of ground state atomic caesium with N,O by direct spectroscopic monitoring in the time domain. CS(~~S,,~) was generated by the pulsed irradiation of caesium chloride vapour in the presence of N,O and excess helium in a static system and monitored by time-resolved atomic resonance absorption spectroscopy in the "single-shot mode" using the resolved Rydberg doublet at h = 455.5 nm (Cs('lp( 2P3,2)) + CS(~S('S~,~)). The spectroscopic source was a newly constructed high intensity, high current hollow cathode source. Photoelectric signals at the resonance wavelength representing the decay of CS(~~S,,~) were captured, digitised and stored in a transient recorder and transferred to a microcomputer for kinetic analysis. The decay profiles were employed to characterise the absolute second-order rate constant k, for the reaction Cs f N,O + CsO + N, across the limited temperature range 847 -865 K, for which we report the average result of k, = (1.9 f 0.3) X lo-" cm3 per molecule s-l. This is compared with those from previous kinetic studies of the reactions between lithium, sodium, potassium and rubidium + N,O derived from direct spectroscopic monitoring in the time domain, and indicate that the reaction with N20 may be employed for titration of atomic caesium in a flow system and for generating CsO in known concentrations for subsequent investigation. An estimate of the diffusion coefficient for caesium in helium of Di2(Cs-He) = about 0.2 cm2 s-i at s.t.p. is reported. Finally, the result is briefly considered in terms of the symmetry of the potential surfaces involved.