Two-photon absorption laser induced fluorescence (TALIF) is applied to atomic oxygen and nitrogen generated in the JAXA 750 kW arc-heated wind tunnel in order to obtain velocity, translational temperature and atomic number density distributions. Free stream velocity is estimated by Doppler shift and the translational temperature distributions are deduced from spectral broadening. The absolute center excitation wavelength and laser line width are estimated with the TALIF profiles from a static reference cell which is called as a flow reactor. In this flow reactor, atomic species are generated by microwave discharge. The spatial distributions of atomic number density are deduced from the integrated TALIF profiles. The absolute atomic number densities inside the flow reactor are estimated with a titration method. From the mass fraction estimation, it is found that the number densities of atomic oxygen are overestimated owing to the saturation effect. When oxygen is assumed to be totally dissociated, the fractional enthalpies are estimated.