Schematic of experimental setup. Exit of the spray nozzle is set at z = 100 mm. Aerosol is ejected downward and spread out at an angle to vertical direction.
The breakdown probabilities of the probe laser and the number density of droplets as a function of the delay time between the pump laser and probe laser. The pump and probe lasers are focused on the same point at the coordinate origin with an interval given by the delay time. The intensities of the pump and probe lasers are 9.2 × 1010 and 1.1 × 1010 [W/cm2] for (a) and 1.5 × 1011 and 2.2 × 1010 [W/cm2] for (b), respectively. The aerosol is ejected at a water flow rate of 10 ml/min and an air pressure of 0.4 MPa at the nozzle for (a), and at a water flow rate of 20 ml/min and an air pressure of 0.1 MPa at the nozzle for (b).
The breakdown probabilities of the probe laser as a function of the delay time for different vertical positions of the breakdown caused by the pump laser. The pump laser is focused at z = 4.0, 3.0, 2.0, 1.0, 0, −0.5, and −1.0 mm for (a), (b), (c), (d), (e), (f), and (g), respectively. Fig. 3(e) is the same result as shown in Fig. 2(a) . The other experimental parameters are thesame as those in Fig. 2(a) . Scales for white legend symbols in (a), (c), (e), and (g) are left hand side and for black ones in (b), (d), and (f) are right hand side, respectively.
The breakdown probabilities of the probe laser as a function of delay time for different horizontal positions of the breakdown caused by the pump laser. The pump laser is focused at x = 2.0, 1.0, and 0 mm for (a), (b), and (c), respectively. Fig. 4(c) is the same result as shown in Fig. 2(a) . The other experimental parameters are the same as those in Fig. 2(a) .
Relationship between the pump laser focus position and the delay time corresponding to the initial decrease in breakdown probability t f, the minimum breakdown probability t b, and the full recovery of the breakdown probability tr as shown in reference diagram, where Pb is the breakdown probability. The solid line is the fitting line for t b. The dashed lines have the same gradient as the solid line, enabling a comparison of the relationships between the distance between the position of the pump laser and the delay times t f and t r.
Distances of plume expansion as a function of expansion time, shown as black points for z-axis and with point for x-axis with experimental errors. These points were obtained from the results shown in Figs. 3 and 4 . The expansion distances take into consideration the aerosol flow velocity and the direction as a vector summation. The dashed line is a best-fitting curve obtained using a drag force model.
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