Radiative decay constants of the H₂ Fulcher bands

The radiative decay constants corresponding to the Fulcher bands of the H2 molecular spectrum are obtained using pulsed-electron beam techniques. Data in the range ∼1.8 to 2.8×107 s−1 are obtained at 25 eV incident electron energy for the d 3πu →a 3Σ+g (v′, v″) Q (K) and k 3πu →a 3Σ+g (v′,v″) Q (K) rotational lines with K=1,2,3 and v′=0,1,2,3,→v″=0,1,2,3. Additional measurements of the d 3πu→a 3Σg+(0,0) Q1 rotational line intensity indicate the presence of a two-mode decay over the energy range 50–300 eV. The long-lived decay component, identified as radiative cascade from upper levels, contributes ∼15% to the total d 3πu(v′=0) population.