SID SENADHEERAMechanical Engineering Department

Ryerson University

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First Experimental Proof of

Raizer–Zeldovich Theorem (or RZ-Theory)

Different methods of producing nanofibers

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Experimental Setup

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Computer simulation of heat dissipation in

laser ablation

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* Initially, the vapor expansion proceeds along the Poisson adiabat with : PVγ = const.

*The Poisson adiabat crosses the saturation adiabat defined by the Clausius-Clapeyron equation.

* The corresponding critical temperature is defined as Tc

P-V diagram with the Causius-Clapeyron equation

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x(t) = (t).g(t)ν

Nucleation rate can be expanded as :

According to RZ-theory the following equation can be written

Condensation rate : dx/dtNucleation rate : dν/dtAtomic clustering rate : dg/dt

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*The sharp increment in nucleation occurs at phase transformation *The time component for Graphite and Silicon can be theoretically graphed as below to estimate the times for phase transformations.

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The first theoretical analysis of condensation dynamics in a rapidly expanding vapor was performed by Raizer et al. in 1958. Anisimov et al. did the next detailed study on the theory with the results below.

(c) Vapor condensation x(t) (f) Atomic clustering g(t)

(b) Supercooling Parameter (e) Cluster dimension variation

(a) Temperature Variations (d) Nucleation rate is ν(t)

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INTRODUCTION TO FEMTOSECOND LASER PULSES

EXPERIMENTAL PROOF OF R-Z THEORY

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* Crystallization and formation of fibers start at a lower pulse frequency for Graphite crystals (less than 1 MHz) and for Silicon (~2MHz)

Graphite Silicon

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Graphite Silicon

Starts nucleation at 1 MHzStarts nucleation at 2 MHz

Interpulse time unit ~ 1 μsInterpulse time unit ~ 0.5 μs*Theoretical estimates (below graph) are in close agreement with the experimental values (above).

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R(t) ~ (Eo/o)1/5 t2/5

Supernova expansion

H-Bomb testing

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Video clip – Please click on picture below

References

[1] K. Venkatakrishnan and B. Tan, “Synthesis of fibrous nano-Structures using ultrafast laser ablation under ambient conditionand at mega hertz pulse frequency,” Optics Express. Jan.(2009)[2] B. N. Chichkov, C. Momma, S. Nolte, F. von Alvensleben, andA. T¨unnermann, “Femtosecond, picosecond and nanosecondlaser ablation of solids,” Applied Physics A, vol. 63, no. 2, pp.109–115, 1996.[3] R. Hergenr¨oder, “A model for the generation of small particlesin laser ablation ICP-MS,” Journal of Analytical Atomic Spectrometry, vol. 21, no. 10, pp. 1016–1026, 2006.[4] B. Rethfeld, V. V. Temnov, K. Sokolowski-Tinten, S. I. Anisimov, and D. von der Linde, “Dynamics of ultrashort pulselaserablation: equation-of-state considerations,” in High-PowerLaser Ablation IV, vol. 4760 of Proceedings of SPIE, pp. 72–80,Taos, NM, USA, April 2002.[5] A. Dalis and S. K. Friedlander, “Molecular dynamics simulationsof the straining of nanoparticle chain aggregates: the caseof copper,” Nanotechnology, vol. 16, no. 7, pp. S626–S631, 2005.[6] S. I. Anisimov and B. S. Luk’yanchuk, “Selected problems oflaser ablation theory,” Physics-Uspekhi, vol. 45, no. 3, pp. 293–324, 2002.[7] S. I. Anisimov, N. A. Inogamov, A. M. Oparin, et al., “Pulsedlaser evaporation: equation-of-state effects,” Applied Physics A,vol. 69, no. 6, pp. 617–620, 1999.[8] B. S. Luk’yanchuk, W. Marine, S. I. Anisimov, and G. A.Simakina, “Condensation of vapor and nanoclusters formationwithin the vapor plume produced by nanosecond laser ablationof Si, Ge and C,” Proc.SPIE, vol. 3618, pp. 434–452, 1999.[9] L. J. Radziemski, R. W. Solarz, and J. A. Paisner, LaserSpectroscopy and Its Applications, CRC Press, Boca Raton, FL,USA, 1987.

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Yakov B. Zeldovich (left), Andrei Sakharov (middle), and David A. Frank-Kamenetskii in Sarov, 1950s

-Russian Academy of Sciences