Direct detection of singlet oxygen O{sub 2}(a{sup 1} {Delta}{sub g}) by absorption at the a{sup 1} {Delta}{sub g} {yields} b{sup 1} {Sigma}{sub g}{sup +} transition using intracavity laser spectroscopy

The absorption spectrum of singlet oxygen O{sub 2}(a{sup 1} {Delta}{sub g}) is detected in a gas phase at the a{sup 1} {Delta}{sub g} {yields} b{sup 1} {Sigma}{sub g}{sup +} transition by the method of intracavity laser spectroscopy using a broad-band Co : MgF{sub 2} laser emitting 200-{mu}s pulses at a wavelength 1.91 {mu}m. In the case of Doppler broadening of absorption lines at room temperature, the sensitivity of detection of O{sub 2} (a{sup 1} {Delta}{sub g}) is {approx} (2 - 5) x 10{sup 14} cm{sup -3} . It is shown that the gas temperature can be calculated from the dependence of absorption cross sections for individual lines on the rotational quantum number. (laser applications and other topics in quantum electronics)