Rotational dependence of the fluorescence quantum yields of H2CO and D2CO (? 1A2): single rovibronic level values and their average values for the 41 level

Abstract

The fluorescence quantum yields, Φ_F(K′, J′), of single rovibronic levels (SRVL’s) of the 4¹ (i.e., ν₄^′=1) vibrational state of H₂CO and D₂CO (? ¹A₂) have been measured at low pressures by laser‐induced fluorescence using a multiple path cell. From these data, the ’’absorption intensity weighted’’ averages of Φ_F are obtained for several K′ rotational manifolds as <Φ_F(K′) 〉 and for the 4¹ level as 〈Φ_F〉. The latter value of 0.031 confirms the validity of the SVL value of 0.0344 obtained from broad‐band optical excitation by Miller and Lee. A random variation of Φ_F (K′, J′) with J′ is observed, and its implication to the question of radiationless transitions in formaldehyde molecules is discussed.