Time-resolved Temperature Inferences Utilizing the TiO A 3 X 3 Band in Laser-induced Plasma

Current efforts involving laser-induced breakdown spectroscopy investigate titanium monoxide (TiO) transitions, inferring temperature for various delay times following laser-induced breakdown. A titanium sample resting in laboratory air is repeatedly exposed to nanosecond pulsed radiation generated by a Nd:YAG laser. Spectral measurements are collected at various delay times ranging from 20 - 95 µs subsequent to the laser event. Temperature inferences at select time delays times are facilitated by fitting synthetic spectra of varying micro-plasma parameters to the gathered spectra utilizing a Nelder-Mead algorithm. In some instances, these inferences provide a temperature versus time profile containing a local minimum, as an increase in the inferred temperature begins at later delay times. This phenomenon, possibly due to combustion, is investigated by analyzing signal to noise ratios with respect to their effect on the inferred temperature of diatomic molecular transitions. Temperature inferences resulting by fitting only regions of the measured spectra believed to be dominated by rotational or vibrational diatomic molecular transitions provide insight into the temporal evolution of the TiO A 3 ��X 3 �, �� = 0 molecular transitions in the laser-induced plasma.