has participant infrared absorption spectroscopy transient infrared spectroscopy Spectroscopy where transient species such as radicals, ions or reactive intermediates are studied using pulses from an infrared laser. The infrared absorbance of the sample before and after an excitation laser pulse is measured. IR transient absorption spectroscopy transient infrared spectroscopy infrared laser transient absorption spectroscopy IR laser transient absorption spectroscopy transient infrared spectrometry FIX:0001068 TIRS infrared transient absorption spectroscopy CHMO:0000642 laser