High precision measurement of ultraweak transitions of the a${}^1{△}_g\leftarrow$X ${}^3{\Sigma }_g^{-}$ $(0,0)$ band of molecular oxygen

Abstract

We have used a highly sensitive cavity-enhanced frequency modulation spectroscopy technique to measure different parameters of the ultraweak transitions of a${}^1{△}_g\leftarrow$X ${}^3{\Sigma }_g^{-}$ $(0,0)$ band of molecular oxygen in the range 7640 cm${}^{-1}$ to 7917 cm${}^{-1}$. The self-broadened half-width and air-broadened half-width of the transitions have been measured for three different pressures for both ${}^{16}$O${}_2$ and ${}^{18}$O${}_2$. To measure the line intensity and self-broadened half-width we have used ultra pure oxygen sample and air-broadened half-width was measured with dry air sample. The $(0,0)$ band of ${}^{16}$O${}_2$ and ${}^{18}$O${}_2$ show weak quadrupole transitions with line intensities ranging from $1\times 10^{-30}$ to $1.9\times 10^{-28}$ cm/molecule. The measurements are in excellent agreement with the recent measurement of Rothman et. al