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Generation of rarefaction and shock waves due to metal-nonmetal transition in laser ablation process
A.A. Samokhin, P.A. Pivovarov
Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991, Moscow, Vavilov str., 38
e-mail: [email protected]
In [1] it was observed additional recoil pressure peak appearance during nanosecond laser ablatioi of liquid Hg. This effect as well as the whole pressure pulse displacement to earlier arrival times wa supposed to be due to metal-nonmetal transition (MNT) in irradiated liquid. The arrival tim< decreasing was observed also in [2,3]. The pressure peak promotes shock wave generation which i responsible for the arrival time diminishing. Combined shock and rarefaction wave structure i analyzed in [4] for quasi-steady-state regime on the basis of conservation laws for mass an< momentum fluxes at shock wave front (1) and rarefaction wave front (2) where MNT occurs.
PoD = pdD-VJ, Po+ PoD2 = Px+ p1(D-V1)2 (1)
p1{d-V1) = P2W-V2), P1+ Pi(d-V{)2 = P2 + P2W-V2)2 (2)
The shock and rarefaction waves are propagating with constant velocities, respectively, D > d > ( in the liquid which was initially at rest in the half-space z > 0 with pressure Po , density po and velocity Vo = 0 with pressure Po , density po and velocity Vo = 0. Between the fronts one has : Vi > 0, Pi > Po and pi > po while after rarefaction wave front V2 < 0 , P2 > Po, and pc < p < P2, where pc means critica density for liquid-vapor phase transition and P2 at the irradiated surface depends on the metal ablatioi
regime conditions. From (1), (2) for m = d/D it follows
1 1 _i
m = 1 -B01+ B012[(P2 - Po)(poD2)-1 + B01 - 1]2(1 - B12) 2 (3)
Fig.1 shows m (Boi) dependence at fixed values of B12 and Boim . It means that shock wave can appear at rather small subsonic d values. Its absolute value can be determined from energy flux conservation law where absorption of laser light should be taken into account. In general case one ha to consider time-dependent problem of laser-metal ablation with strong decreasing of laser ligh absorption coefficient due to MNT. Such theoretical and experimental investigations are necessary fo obtaining new information about metal critical parameters manifestations in non-equilibrium conditions of laser ablation [1,5].
Fig.1 Dependencies of the value m on the ratio Bo1=po/p1 for three fixed ratio B12=p1/p2 and one fixed ratio (P2 - Po)/ poD2 =1-Bo1M= 3.51C
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2. A.A. Samokhin, E.V. Shashkov, N.S. Vorobiev, A.E. Zubko, On acoustical registration of irradiated surface displacement during nanosecond laser-metal interaction and metal-nonmetal transition effect, Appl. Surf. Sci., 502, 144261 (2020).
3. S.I. Kudryashov, S. Paul, K. Lyon, S.D. Allen, Dynamics of laser-induced surface phase explosion in silicon, Appl. Phys. Lett. 98 2541C (2011)
4. A.A. Samokhin, P.A. Pivovarov, On the mathematical model of combined rarefaction and compression waves in condensed matter, Mathematica Montisnigri, 50, 104-107 (2021)
5. I. Iosilevskiy, V. Gryaznov, Uranium critical point location problem, Zababakhin Scientific Talks (International Conference) March 1822 95 (2019).
