High-resolution one-photon absorption spectroscopy of the $D\,{}^2\Sigma^- \leftarrow X\,{}^2\Pi$ system of radical OH and OD

摘要

Vacuum-ultraviolet (VUV) photoabsorption spectra were recorded of the$A\,{}^2\Sigma^+(v'=0)\leftarrow{}X\,{}^2\Pi(v''=0)$,$D\,{}^2\Sigma^-(v'=0)\leftarrow{}X\,{}^2\Pi(v''=0)$ and$D\,{}^2\Sigma^-(v'=1)\leftarrow{}X\,{}^2\Pi(v''=0)$ bands of the OH and ODradicals generated in a plasma-discharge source using synchrotron radiation asa background continuum coupled with the VUV Fourier-transform spectrometer onthe DESIRS beamline of synchrotron SOLEIL. High-resolution spectra permittedthe quantification of transition frequencies, relative $f$-values, and naturalline broadening. The $f$-values were absolutely calibrated with respect to aprevious measurement of $A\,{}^2\Sigma^+(v'=0)\leftarrow{}X\,{}^2\Pi(v''=0)$([wang1979]). Lifetime broadening of the excited $D\,{}^2\Sigma^-(v=0)$ and$D\,{}^2\Sigma^-(v=1)$ levels is measured for the first time and compared withprevious experimental limits, and implies a lifetime 5 times shorter than atheoretical prediction ([van_der_loo2005]). A local perturbation of the$D\,{}^2\Sigma^-(v=0)$ level in OH was found.