We report studies on the multiple ionization of the N₂ molecule using intense, femtosecond laser pulses. We present details of the experimental characterisation of the light pulses and analysis and detection of the ions produced. Precautions to be taken in intense field ionization experiments are discussed. We illustrate the retrieval of information about different aspects of the ionization process (such as, kinetic energies of the fragments produced, dissociation bond lengths and information on the precursors to fragmentation) using coincidence techniques. We report results of the first measurements of the angular distribution of a highly charged fragment, N³⁺.

This article presents an overview of the physics and applications of the interaction of high intensity laser light with matter. It traces the crucial advances that have occurred over the past few decades in laser technology and nonlinear optics and then discusses physical phenomena that occur in intense laser fields and their modeling. After a description of the basic phenomena like multiphoton and tunneling ionization, the physics of plasma formed in dense matter is presented. Specific phenomena are chosen for illustration of the scientific and technological possibilities – simulation of astrophysical phenomena, relativistic nonlinear optics, laser wakefield acceleration, laser fusion, ultrafast real time X-ray diffraction, application of the particle beams produced from the plasma for medical therapies etc. A survey of the Indian activities in this research area appears at the end.

Efficient low debris hard X-ray source based on multiwalled carbon nanotubes (MWNT) irradiated by intense, femtosecond laser over an intensity range of $10^{15} –10^{17}$ W cm$^{−2} \mu𝑚^{2}$ is reported. The MWNT targets yield two orders of magnitude higher X-rays (indicating significant enhancement of laser coupling) and three orders of magnitude lower debris compared to conventional metallic targets under identical experimental conditions. The simple analytical model explains the basic experimental observations and also serves as a guide to design efficient targets to achieve low-debris laser plasma-based hard X-ray sources at low laser intensities suitable for multi-kHz operation.