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The present work is devoted to the precise spatiotemporal mapping of the absolute density of Ar(1s5) in a ns‐pulsed argon plasma jet. The plasma impinges on glass and alumina targets at floating potential placed 5 mm away from the reactor's nozzle. Under these conditions, diffuse discharges are established in the small gas gap. As so, the line‐of‐sight absolute density of Ar(1s5) is effectively evaluated via laser absorption spectroscopy. The application of the Abel‐inversion is also demonstrated for different operating conditions leading to the precise radial mapping of the Ar(1s5) absolute density. The influence of each target is studied for two gas flow rates, 0.3 and 0.4 l min−1. The temporal density profiles over a voltage pulse period reveal two maxima related with the Ar(1s5) production in the streamer head and in the residual diffuse plasma channel. Furthermore, the maximum Ar(1s5) axial/radial density (∼1013 − 3.5 × 1014 cm−3) depends on the target material and gas flow rate. Finally, the plasma is proved to be very effective for the fast desorption of organic molecules (bibenzyl) deposited on both targets. The results obtained suggest that the desorption of bibenzyl is due to the production of high Ar(1s5) densities at the close vicinity of the targets. Argon plasma jets (APJs) have been poorly studied for the detection of weakly volatile substances (of interest for different applications). Hereby, an APJ is optimized for the desorption of organic molecules (bibenzyl) deposited on different dielectric plates. The experiments are focused on the accurate quantification of argon metastables spatial (axial‐radial) and temporal densities, suggesting their implication on the desorption process. [ABSTRACT FROM AUTHOR]