Study On Ultrafast Probing And Controling Of Quantum States Evolutive Dynamics For Cu Atom And NaI Molecule

The dynamical evolution of copper quantum states in recombination processes of plasma induced by nanosecond laser pulse were investigated systematically by time-resolved spectrum. Meanwhile, the processes of generating plasma and ablating target surface were also monitored by ultrafast exposal imaging with femtosecond laser pulse. The results revealed that copper plasma appeared firstly during nanosecond laser irradiating target surface. The density of copper plasma got its maximum value several tens of nanoseconds later. The copper surface ablation appeared at the time of a nanosecond laser pulse gone completely about 110ns later. The process of copper target ablation lasted for 560ns. It was proved that heat deposition from plasma after laser disappearing was the main mechanism of solid-liquid phase transition. There were 74 copper quantum states including doublets and quartet states which were found in recombination processes of laser inducing plasma. The producing mechanism and dynamical evolution of even quantum states 4d′4F9/2 and 5s′4D7/2 were studied in detail. The most important time domains for producing the two quantum states were 50-400ns and 25-200ns respectively in the early stage of copper plasma recombination. Deexcitation of quantum states with high energy and excitation of quantum states with low energy through collision among particles would be the main mechanism of generating the two quantum states in the middle and later stage of plasma recombination.The predissociation process of NaI was simulated with semi-classical model of ultra-short laser pulse interacting with molecules. Meanwhile the predissociation branching ratio of NaI was mainly investigated after the control pulse was introduced. The results elucidated that the amount of Na atoms dissociated from NaI ascented with up stairs when the wavelength of pump laser was set to 324nm. Meanwhile the population probability flux density at ground state attenuated oscillately. The initial population probability at excited state was influenced when the peak power density of pump laser pulse changed, but the predissociation branching ratio of NaI would remain unchanged. The oscillation period and the branching ratio of NaI maintained as the pulse duration of pump laser changed in the range of 0-100fs. But the branching ratio of NaI would decrease slightly when the pulse duration of pump laser became long enough so that it could affect the coupling zone. Not only the initial population probability at both excited and ground state but also the predissociation branching ratio of NaI was affected directly when the wavelength of pump laser pulse was adjusted. The predissociation branching ratio would be manipulated distinctly when the control pulse was introduced during the oscillation of NaI. The time delay between pump and control pulses can affecte the predissociation branching ratio of NaI distinctly, and it would become significantly higher when the time delay was adjusted to 100-150fs. The branching ratio of NaI would increase firstly and then decrease as the pulse duration of control pulse was increased. The branching ratio would get an optimal value when it was set to 100fs. The population probability of NaI at ground and excited states can also be manipulated distinctly as adjusting both the wavelength and peak power density of control pulse. The branching ratio of NaI would increase firstly and then decrease as the wavelength of control pulse was increased. But the branching ratio of NaI would ascent oscillately as the peak power density was increased.