Experimental verification of the Einstein A-coefficient used for evaluation of O-2((1)Delta(g)) concentration in the chemical oxygen-iodine laser

This paper is a contribution to the current discussion on the Einstein coef ficient for spontaneous emission (A-coefficient) of singlet delta oxygen, O -2((1)Delta(g)), that is often used for an evaluation of O-2((1)Delta(g)) c oncentration in a chemical oxygen-iodine laser (COIL). The published values of the A-coefficient vary in a wide range, corresponding to a radiative li fetime of O-2((1)Delta(g)), tau(Delta)(rad), from similar to 53 to similar to 151 min. This could make an evaluation of COIL operation questionable. I n this paper, the Einstein A-coefficient is estimated, based on the compari son of O-2((1)Delta(g)) concentrations determined by two independent method s: electron paramagnetic resonance and emission spectroscopy. Within the ac curacy of the experimental techniques used, the value of the A-coefficient resulting from our investigation is (2.24 +/- 0.40) x 10(-4) s(-1), corresp onding to tau(Delta)(rad) of similar to 74 min. This result is more consist ent with the value of 2.58 x 10(-4) s(-1) of Badger et al III than with the value of 1.47 x 10(-4) s(-1) reported recently by Mlynczak and Nesbitt [2] , who raised doubt about the Badger er al value.