SID SENADHEERA Mechanical Engineering Department Ryerson University

1. First Experimental Proof of Raizer–Zeldovich Theorem (or RZ-Theory) SID SENADHEERAMechanical Engineering DepartmentRyerson University

2. Different methods of producing nanofibers

3. Experimental Setup

10. Computersimulation of heat dissipation in laser ablation

11. * 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

12. 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 :

13. *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.

14. 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)

15. EXPERIMENTAL PROOF OF R-Z THEORY INTRODUCTION TO FEMTOSECOND LASER PULSES

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

19. 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).

20. R(t) ~ (Eo/ro)1/5 t2/5 R R R Supernova expansion R H-Bomb testing

21. Video clip – Please click on picture below

22. 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.

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