The effect of air pressure on the IR spectral emission from laser induced air plasma

The IR emission from laser induced air plasma under pressure of 20 similar to 100 kPa has been investigated in the 1100 similar to 2400 nm region. The results show that the IR spectra of air plasma consist of line spectra and continuum radiation. Most of the spectral features observed from laser induced air plasma are identified as atomic lines of OI, N I and molecular bands of N-2, and the continuum radiation in the IR spectrum from air plasma mainly origins from the blackbody emission. It is found that IR line emission intensity depends strongly on the temperature of plasma as well as the pressure of air. Furthermore, time of flight (TOF) study of plasma emission show that temporal evolution of spectral lines at NI 1358 nm and N-2 band 2252 nm under different pressures are with asymmetric shapes. Underlying physics responsible for the asymmetric shapes of TOF spectra is discussed.