Transient Dynamics Of The Excited State 5s’⁴D_7/2 Of Copper Atom In Femtosecond Laser Induced Plasma Recombination

Recently, with gradually developing of ultrafast laser technology, time-resolved spectroscopy technology in ultrafast dynamics fields, had become one of research highlights in the world and was applied in diagnosing and testing of many ultrafast processes. So it was significant to investigate the excited state of atom and how to construct a precise time-resolved spectroscopy measuring system.In this paper, the time-resolved spectroscopy technology of femtosecond laser interact with copper atom for high-precision measurement was investigated in both theoretically and experimentally. Time-resolved measuring system was constructed based on basic theories of time-resolved spectroscopy technology and laser induced plasma technology. After a series of experiments, expected results were acquired and the effectiveness of the time-resolved spectroscopy measuring system was verified.Main achievements in this paper were listed as follows:1. Time-resolved spectroscopy measuring system was established with femtosecond laser as light source and its resolution was in picosecond order.2. Basic theory about the excited state 5s′4D7/2 of copper atom in transition process and the relationship between the polarization state of femtosecond laser and temporal behavior of plasma were described. According to measure the intensity evolution of Cu-I and Cu-II lines, the ultrafast dynamics temporal behavior of 5s′4D7/2of copper atom was measured. And interestingly, We find the Cu-I and Cu-II lines appearing at t=40 and t=65 ns, respectively, and the peak intensity of continuous spectrum appearing at t=20 ns, which were independent of the laser intensity. The lifetime of Cu-I and Cu-II were linear fit with the laser intensity. The electron temperature was 8000 K~4500 K and maximum electron density was18 32.9 10 cm??with the laser power at 2.4 W.3. According to measure the different polarization states of laser interact induced plasma, our findings build on linear polarization suggest that the intensity、lifetime、stark broadening and frequency shift of Cu-I and Cu-II lines with circular polarization were larger than linear polarization laser induced plasma. The electron temperature was 9500 K~5000 K and maximum electron density was18 34.5 10 cm?? with thecircular polarization laser power at 2.4 W. Under elliptical polarization laser filed, the intensity of Cu-I and Cu-II lines increase with the laser ellipticity.4. In the double pulse laser induced plasma experiment, the first we demonstrate the effectiveness of our experimental system. At the interval of double pulse was 2 ns~4 ns, the intensity of Cu-I and Cu-II lines was low than single pulse laser induced plasma. They had the same stark broadening and frequency shift.