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ultrafast-lasers
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Efficient photo-dissociation of CH4 and H2CO molecules with optimized ultra-short laser pulses
, Article AIP Advances ; Volume 5, Issue 11 , 2015 ; 21583226 (ISSN) ; Irani, E ; Sadighi Bonabi, R ; Sharif University of Technology
American Institute of Physics Inc
2015
Abstract
The fragmentation dynamics of CH4 and H2CO molecules have been studied with ultra-short pulses at laser intensityof up to 1015Wcm-2. Three dimensional molecular dynamics calculations for finding the optimized laser pulses are presented based on time-dependent density functional theory and quantum optimal control theory. A comparison of the results for orientation dependence in the ionization process shows that the electron distribution for CH4 is more isotropic than H2CO molecule. Total conversion yields of up to 70% at an orientation angle of 30o for CH4 and 65% at 900 for H2CO are achieved which lead to enhancement of dissociation probability
Controlling the properties of TiO2 nanoparticles generated by nanosecond laser ablation in liquid solution
, Article Laser Physics ; Volume 28, Issue 8 , 2018 ; 1054660X (ISSN) ; Irani, E ; Golzan, M. M ; Sadighi Bonabi, R ; Sharif University of Technology
Institute of Physics Publishing
2018
Abstract
Laser ablation of titanium target in distilled water for synthesis of colloidal nanoparticles is studied both experimentally and theoretically. The effects of laser parameters such as wavelength, pulse energy, fluence and shot numbers on the ablation rate and size properties of colloidal nanoparticles are investigated. The experimental approach addresses the interesting issue for finding the optimal main experimental parameters of laser ablation. The theoretical thermal model of nanosecond pulsed laser ablation is developed to visualize the evolution of temperature distributions and ablation depth. The simulation result of ablation depth has been compared with the experimental result...
Multielectron dissociative ionization of methane and formaldehyde molecules with optimally tailored intense femtosecond laser pulses
, Article Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy ; Volume 185 , 2017 , Pages 298-303 ; 13861425 (ISSN) ; Anvari, A ; Sadighi Bonabi, R ; Monfared, M ; Sharif University of Technology
Abstract
The multielectron dissociative ionization of CH4 and CH2O molecules has been investigated using optimum convolution of different dual tailored short laser pulses. Based on three dimensional molecular dynamics simulations and TDDFT approach, the dissociation probability is enhanced by designing the dual chirped-chirped laser pulses and chirped-ordinary laser pulses for formaldehyde molecule. However, it is interesting to notice that the sensitivity of enhanced dissociation probability into different tailored laser pulses is not significant for methane molecule. In this presented modifications, time variation of bond length, velocity, time dependent electron localization function and evolution...
Optimization of two tailored rectangular femtosecond laser pulses in methane dissociation
, Article Proceedings of SPIE - The International Society for Optical Engineering, 12 April 2010 through 16 April 2010 ; Volume 7721 , April , 2010 ; 0277786X (ISSN) ; 9780819481948 (ISBN) ; Dehghani, Z ; Irani, E ; The Society of Photo-Optical Instrumentation Engineers (SPIE); Brussels Photonics Team (B-PHOT); Brussels-Capital Region; Fonds Wetenschappelijk Onderzoek (FWO); International Commission for Optics (ICO) ; Sharif University of Technology
2010
Abstract
Based on the quantum mechanics principles and classically calculated dressed potential surfaces by using field assisted dissociation model the dissociation probability for CH4 + molecule exposed with a 100 femtosecond 8 Jcm-2 Ti:sapphire laser pulses is calculated. Using the gradient optimization method two tailored rectangular laser pulses for controlling the dissociation of C-H bond of CH4 + molecule along laser pulse direction is found. In the proposed optimization method, the complicacy of solving Schrodinger wave equation is reduced by using classical method and in contrast to the usual controlling and pulse shaping methods of chemical reactions, the experimental data is not needed and...