The results of remote detection of objects containing explosives with a lidar detector of traces of explosives in combination with a portable express gas chromatograph are presented. It is...

The paper presents the results of an experimental study of the dynamic characteristics of the laser fragmentation/laser-induced fluorescence (LF/LIF) effects in nitrobenzene vapors under the separate initiation of processes of photofragmentation and fluorescence of fragments by nanosecond laser pulses. It is shown that, due to the inertia of the dissociation mechanism of nitrobenzene molecules, the process of the fragments’ formation continues even after letup of excitation. The highest concentration of fragments is reached in a time several times greater than the standard fragmentation pulse duration of 10 ns. A kinetic model is presented that allows one to trace the temporal dynamics of the LF/LIF process of nitrobenzene vapors under separate excitation. A good agreement between the experimental data and the results of calculation indicates the adequacy of application of the developed kinetic model for describing the LF/LIF process. The information obtained in the experiment made it possible to clarify the values of the rate constants of the nitrobenzene dissociation.

Results of calculation of the absorption spectrum of phosphorus oxide (PO) corresponding to the A²Σ⁺ (v′ = 0) − X ²Π (v′′ = 0) transition are presented. The calculation is performed taking into account the perturbation of the v′ = 0 level of the A²Σ⁺ state by the v′ = 4 level of the b⁴Σ⁻ state. The efficiency of laser excitation of PO molecules is estimated as a function of the spectral parameters of the radiation. The time dependence of the efficiency of the excitation of PO fragments is calculated for a real atmosphere under two-pulse laser fragmentation of organophosphates for specified spectral linewidths Δλ and center positions λ₀.

The paper presents the results of a numerical evaluation of limiting sensitivity of the method for detecting vapors of nitrocompounds in the atmosphere based on one-color laser fragmentation (LF)/laser-induced fluorescence (LIF) of NO fragments via A²Σ⁺ (v′ = 0) ← X²Π (v″ = 2) transition. The calculations were performed using the developed kinetic model of the one-color LF/LIF process under consideration. The calculations take into account the influence of ambient nitrogen dioxide as a limiter of the sensitivity of the method when operating in a real atmosphere. It is shown that if the nitrogen dioxide concentration in the atmosphere does not exceed a value of 10 ppb, the maximum detectable vapor concentrations of nitrobenzene and o-nitrotoluene are several ppb. It is also shown that the method of single-frequency one-color excitation usually used for the detection of nitrocompounds does not allow achieving the maximum efficiency of the LF/LIF process.

The techniques for alignment and quality checking of the primary 2.2-m diameter mirror of the Siberian lidar station (SLS) are suggested. The results of computer simulation of the field aberrations of the primary mirror are presented, and the area of the coma-free region is estimated. The spot diagram of the SLS primary mirror is measured based on the estimates of the image size of stars transiting through the zenith. Lidar signals are numerically simulated using ray tracing in the optical design program ZEMAX, accounting for the effect of the real spot diagram of the receiving optics. The shapes of the experimentally recorded and ray tracing simulated lidar signals are compared.