Knowledge Bank

We have utilized the nanosecond pulse time structure of ACO synchotron radiation to record fluorescence decay curves from isolated CO molecules in the $A1\Pi$ electronic state. With broad band excitation ($\sim$10 {\AA}) the fluorescence decay from single vibronic levels was found to be generally nonexponential. Under a narrow band excitation $(0.3\backslash AA)$ pumping a few rovibronic levels, the form of decay depends on $\lambda exc$ within a vibronic band contour. These effects are due to the perturbations of the $A1\Pi$ levels by neighboring levels belonging to the and $d3\Delta$ triplet states. By assuming the wave functions of individual rovibronic states as: $$| n> = a|s>+ \Sigma_{i} b_{i}|t_{i}>$$ (where a and $bi$ are determined by analysis of perturbations) and their radiatives rates as: $\gamma n=a2\gamma S$ (where $YS$ is the radiative rate of the ``pure” singlet vibronic level) we obtained computer simulations of decay curves. From the best fits of calculated and experimental curves, the values of $YS$ for vibronic levels $v=0$ to 7 were determined and their dependence on v and on the r-centroid will be discussed.""