Investigation of the collision-induced absorption by O-2 near 6.4 mu m in pure O-2 and O-2/N-2 mixtures

The collision-induced fundamental vibrational band of molecular oxygen has been measured between 1300 and 2000 cm(-1) using a Fourier-transform infrar ed spectrometer and an optical path length of 84 m. Spectra were recorded f or pure O-2 and O-2/N-2 mixtures at densities up to 10 times the density of an ideal gas at standard temperature (273.15 K) and pressure (101.325 kPa) , and for temperatures between 228 and 296 K. The band is dominated by the Delta J = 0, Q branch and the Delta J = 2, S and Delta J = -2, O branch sho ulders, with the S branch exhibiting ripples previously attributed to bound dimer transitions, pure quadrupole transitions of O-2 perturbed by line mi xing, and intercollisional interferences. The ripples are seen at the same wavenumbers in O-2-Ar mixtures, with intensities dependent on both the O-2 and Ar densities, suggesting that the ripples are not due to bound dimer tr ansitions. The integrated band intensity S is related to the collision-indu ced absorption coefficients by S = S(O2-O2)rho(O2)(2) + SO2-N2 rho(O2)rho(N 2), where SO2-O2 and SO2-N2 are the integrated binary collision-induced abs orption coefficients for O-2-O-2 and O-2-N-2 collisions, respectively, and rho(O2) and rho(N2) are the O-2 and N-2 gas densities. We find values for S O2-O2 = 6.972(66) X 10(-4) cm(-2) and SO2-N2 = 7.12(22) X 10(-4) cm(-2) res pectively, at 296 K,when the gas density is equal to that found at STP (i.e ., SO2-O2 6.972(66) X 10(-4) cm(-2) amagat(-2) and SO2-N2 = 7.12(22) X 10(- 4) cm(-2) amagat(-2)).