Time-resolved spectroscopy for 5s'⁴D_7/2 state transitions undergoing electron-ion recombination in femtosecond laser-produced copper plasma

In the femtosecond laser-produced Cu-plasma, the transient transition dynamics that the excited state 5s'⁴D_7/2 via electron-ion recombination transfers to 4p'⁴F_9/2⁰ (465.11 nm, Λ₁ line) and 4p'⁴D_7/2⁰ (529.25 nm, Λ₂ line) states are investigated by using the time-resolved spectroscopy. The occupation number and relevant lifetime of the excited state 5s'⁴D_7/2, the temporal evolutions of spectral intensities for Λ₁ line and Λ₂ line emissions are demonstrated to be in direct proportion to the employed laser intensity, which reveals the transient features of transition dynamics clearly differing from that resulted in the traditional collision excitation. Furthermore, some unique characteristics for Λ₁ and Λ₂ transitions stemming from electron-ion recombination are examined in detail.