Time-resolved emission spectroscopy in laser-generated nitrogen plasmas

Extremely high-lying states of atomic and molecular nitrogen ions have been observed and analyzed in the transient plasma that results from focusing a Q-switched Nd:YAG (where YAG denotes yttrium aluminum garnet) laser into a pure nitrogen atmosphere ranging in pressure from 100 to 800 Torr. During the first 10 to 80 ns after plasma ignition several states of N³⁺ can be detected. Their Stark broadened linewidth is strongly time dependent due to the rapidly changing electron density in the decaying plasma. At around 20 to 40 {μ}s after plasma ignition, rotationally resolved emission in the first negative system of N₂⁺, ²Σᵤ⁺{→}X ²Σg⁺ indicates a rotational and vibrational temperature of about 9500 K. No significant interference from the second positive system C³{{{Π}}}ᵤ→B³{{Π}}g$ of the neutral molecule is observed. Under these conditions rotational levels up to N'=112 in the R branch of the (0,0) band have been identified. In this band, new perturbations at around N'=82 and 95 due to the v=12 and 13 vibrational levels of the A²{{{Π}}}ᵤ$ state are reported.