Femtosecond; Laser repetition rate; Limit of detection;INDUCED BREAKDOWN SPECTROSCOPY; NANOSECOND

Experimentally investigated limit of detection Mg, Al, Sr, Pb. depending on the pulse repetition rate femtosecond Ti: Sa laser optical breakdown in aqueous solutions on the surface of the investigated element in the laser pulse duration 60 fs, pulse energy of 1 mJ. The study was conducted for the laser pulse repetition rate of 50 Hz, 150 Hz, 250 Hz. To choose the optimal time delay of registration relative to the laser beam for the following chemicals:: Na, N, Fe, Ca, Mg, Al, Pb, Mn.

SPECTROSCOPY; INTENSITY; LINES; WATER

Temporal behavior of the intensity of Ba I emission lines (413.24 and 553.55 nm) in plasma of optical breakdown induced by femtosecond laser pulses (800 nm, 45 fs, 0.82 mJ) on the surface of BaCl2 aqueous solution was experimentally studied as dependent on delay time t (d) relative to the breakdown onset. The maximum intensity of the Ba I (413.24 nm) line was observed at t (d) = 20 ns, while the intensity of the Ba I (553.55 nm) line reached a maximum at t (d) = 40 ns. At t (d) = 10 ns, the intensity of the Ba I (413.24 nm) line was almost three times as large as that of Ba I (553.55 nm) line (despite the about two orders of magnitude lower probability of spontaneous transition for the former line), which is explained by the recombination cascade. It is established that, in the subsystem of 5d6p (3) D (0) and 6s6p (1) P (0) levels, the Boltzmann distribution is not valid and the local thermodynamic equilibrium is absent.