The dalby system of iodine revisited: Rotationally resolved (2 + 1) rempi spectra of the rydberg state [2Π_1/2]_c6s;1g of i₂

Partly rotationally resolved (2 + 1) resonance-enhanced multiphoton ionization spectra of the vibrational hands in the Dalby system ([2Π_1/2]_c6s;1g ← X) of I₂(g) have been recorded and analyzed at room temperature. The simulation technique used in spectral analyses is described and discussed. A statistical weight ratio of odd total nuclear spin: even total nuclear spin = 7:5 is clearly seen from the same relative intensities for rotational lines corresponding to odd J″:even J″ transitions. Rotational constants (B_v′ and D_v′) and corresponding internuclear distances (r_v′) for the Rydberg state ([2Π_1/2]_c6s;1g) are obtained, as well as the characteristic rotational parameters B′_e = 0.04036 ± 0.00001 cm^-1, α′_e = (1.12 ± 0.02) × 10^-4 cm^-1, and r′_e = 2.5656 ± 0.0005 Å. Vibrational analyses based on determination of band origins from the spectral simulations were performed to obtain ω_e = 241.8 ± 0.5 cm^-1 and ω_ex_e = 0.64 ± 0.07 cm^-1, in good agreement with earlier results by Dalby et al. (Can. J. Phys.55, 1033-1046, 1977).