Title:	Nanosecond and FemtosecondLaser Produced Aluminum Plasmas: A Comparitive Study
Authors:	Sankar, Pranitha Nivas, Jijil JJ Smijesh, N Philip, Reji
Issue Date:	Dec-2014
Publisher:	Conference on Plasma Science and Technology (PLASMA 2014)
Citation:	Conference on Plasma Science and Technology (PLASMA 2014), 8-11 December, 2014, p199; 29th National Symposium on Plasma Science and Technology & International
Abstract:	Optical emission spectroscopy1 (OES) and optical time of flight2 (OTOF) studies of laser produced plasmas (LPP) generated by irradiating an Aluminum target by ultrafast (100fs, 800nm) and short (7ns, 1064nm)laser pulsesat5 Torr nitrogenbackground pressure have been carried out for various laser fluences. Electron temperatures have been calculated from the line intensities measured from the emission spectra, and electron number densities have been estimated from the measured spectral linewidths. It is found that the electron temperature increases with fluence for ns excitation, while it remains nearly a constant for fs irradiation. This temperature increase is attributed to photoionization and inverse bremsstrahlung processes.Optical time of flight studies reveal the occurrence of two successive peaks (fast and slow, respectively) in the emission dynamics of neutrals for ns excitation. On the other hand, only one peak (the slow peak) is observed in the case of fs excitation. The arrival time of the fast peak remains almost the same with laser fluence, but the slow peak gets delayed in time with fluence. It is shown that the fast peak corresponds to recombined neutrals while the slow peak arises from un-ionized neutrals, similar to OTOF findings reported in certain recent papers3,4. Results are analyzed on the basis of fundamental differences pertaining to the generation of ultrafast and short-pulse laser plasmas.
Description:	Restricted Access.
URI:	http://hdl.handle.net/2289/8491
Alternative Location:	http://arxiv.org/abs/ http://dx.doi.org/
Copyright:	2014, PLASMA
Appears in Collections:	Research Papers (LAMP)

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