Abstract

The second harmonic (532 nm) of a pulsed Nd:YAG laser with a pulse width of 10 ns and an energy maximum of 300 mJ/ pulse was used to induce combustion on a rotating coal target prepared by compressing powdered coal to 15,000 psi in a die. The spectrum was recorded with a double monochromator coupled with a Hamamatsu P636 photomultiplier and a boxcar integrator. The B²Σ⁺ – X²Σ⁺ system of CN at 3883 Å involving transitions (0,0), (1,1), (2,2), (3,3), and (4,4) was observed. The Swan system of C₂ corresponding to d³ II_g–a³II_u involving (1,0), (2,1), (3,2), (4,3), (6,5), (0,0), and (1,1) transitions were prominent. The bands of the B¹Σ⁺–A^lII angstrom system of CO involving (0,1) and (0,2) transitions were also recorded. The resonance doublets of sodium and potassium atoms have also been observed in the laser-induced combustion. It is found that the relative intensities of the band systems among themselves as well as in relation to those of the alkali doublets changed with experimental conditions indicating their dependence on laser power and therefore on temperature.

© 1989 Optical Society of America