Spectroscopy study of air plasma induced by IR CO2 laser pulses

• DOI: 10.1007/s00339-009-5466-x
• Publication Date: 2009-11-06T16:11:11Z
• Authors: J. J. Camacho; M. Santos; L. Díaz; L. J. Juan; J. M. L. Poyato
• Keywords: 13. Climate action; 0103 physical sciences; 01 natural sciences; 7. Clean energy

A spectroscopic study of ambient air plasma, initially at room temperature and pressures ranging from 32 to 101 kPa, produced by high-power transverse excitation atmospheric (TEA) CO2 laser (λ = 9.621 and 10.591 μm; τFWHM ≈ 64 ns; power densities ranging from 0.29 to 6.31 GWcm-2) has been carried out in an attempt to clarify the processes involved in laser-induced breakdown (LIB) air plasma. The strong emission observed in the plasma region is mainly due to electronic relaxation of excited N, O and ionic fragments N+. The medium-weak emission is due to excited species O+, N2+, O2+, C, C +, C2+, H, Ar and molecular band systems of N + 2 (B2Σ + u -X 2Σ + g), N2(C 3Πu- B3Πg), N+ 2 (D2Πg-A2Πu) and OH(A2Σ +-X2Π). Excitation temperatures of 23400 ± 700 K and 26600 ± 1400 K were estimated by means of N+ and O+ ionic lines, respectively. Electron number densities of the order of (0.5-2.4)×1017 cm-3 and (0.6-7.5)×1017 cm-3 were deduced from the Stark broadening of several ionic N+ and O+ lines, respectively. Estimates of vibrational and rotational temperatures of N+ 2 electronically excited species are reported. The characteristics of the spectral emission intensities from different species have been investigated as functions of the air pressure and laser irradiance. Optical breakdown threshold intensities in air at 10.591 μm have been measured. © Springer-Verlag 2009. We gratefully acknowledge the support received by the DGICYT (Spain) Projects: MEC: CTQ2008-05393/BQU and MEC: CTQ2007-60177/BQU for this research. Peer Reviewed