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First Experimental Proof of Raizer–Zeldovich Theorem (or RZ-Theory). SID SENADHEERA Mechanical Engineering Department Ryerson University. Different methods of producing nanofibers. Experimental Setup. Computer simulation of heat dissipation in laser ablation.

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SID SENADHEERA Mechanical Engineering Department Ryerson University

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Presentation Transcript

First Experimental Proof of

Raizer–Zeldovich Theorem

(or RZ-Theory)

Different methods of producing nanofibers

Experimental Setup

Computersimulation of heat dissipation in laser ablation

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

P-V diagram with the Causius-Clapeyron equation

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

• * The corresponding critical temperature is defined as Tc

According to RZ-theory the following equation can be written

Condensation rate : dx/dt

Nucleation rate : dν/dt

Atomic clustering rate : dg/dt

x(t) = ν(t).g(t)

Nucleation rate can be expanded as :

*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.

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.

(a) Temperature Variations

(d) Nucleation rate is ν(t)

(b) Supercooling Parameter

(e) Cluster dimension variation

(c) Vapor condensationx(t)

(f) Atomic clustering g(t)

EXPERIMENTAL PROOF OF R-Z THEORY

INTRODUCTION TO FEMTOSECOND LASER PULSES

Graphite Silicon

* Crystallization and formation of fibers start at a lower pulse

frequency for Graphite crystals (less than 1 MHz) and for Silicon (~2MHz)

Silicon

Graphite

Starts nucleation at 2 MHz

Starts nucleation at 1 MHz

Interpulse time unit ~ 0.5 μs

Interpulse time unit ~ 1 μs

*Theoretical estimates

(below graph) are in close agreement with the experimental values (above).

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

R

R

R

Supernova expansion

R

H-Bomb testing

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 condition

and at mega hertz pulse frequency,” Optics Express. Jan.(2009)

[2] B. N. Chichkov, C. Momma, S. Nolte, F. von Alvensleben, and

A. T¨unnermann, “Femtosecond, picosecond and nanosecond

laser 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 particles

in 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 pulselaser

ablation: equation-of-state considerations,” in High-Power

Laser 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 simulations

of the straining of nanoparticle chain aggregates: the case

of copper,” Nanotechnology, vol. 16, no. 7, pp. S626–S631, 2005.

[6] S. I. Anisimov and B. S. Luk’yanchuk, “Selected problems of

laser ablation theory,” Physics-Uspekhi, vol. 45, no. 3, pp. 293–

324, 2002.

[7] S. I. Anisimov, N. A. Inogamov, A. M. Oparin, et al., “Pulsed

laser 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 formation

within the vapor plume produced by nanosecond laser ablation

of Si, Ge and C,” Proc.SPIE, vol. 3618, pp. 434–452, 1999.

[9] L. J. Radziemski, R. W. Solarz, and J. A. Paisner, Laser

Spectroscopy and Its Applications, CRC Press, Boca Raton, FL,

USA, 1987.

Yakov B. Zeldovich (left), Andrei Sakharov (middle),

and David A. Frank-Kamenetskii in Sarov, 1950s