摘要： Rotationally resolved spectra of the H3Σ?u - X3Σ?g electronic transition bands of Si2 have been experimentally studied using laser induced fluorescence in the 380 - 520 nm range. Si2 molecules are produced in a supersonically expanding planar plasma by discharging a silane/argon gas mixture. In total 44 bands belonging to the H3Σ?u - X3Σ?g electronic transition system of the most abundant isotopologue 28Si2 are experimentally recorded. With a spectral resolution ～ 0.04 cm?1, the triplet spin-splitting structures in individual rotational transition lines are fully resolved. Detailed analyses on the high resolution spectra have yielded an accurate determination of spectroscopic constants for both X3Σ?g and H3Σ?u states. The spin-spin interaction constants for the two triplet states are found to be comparable (λ ～ 1.5 cm?1), which may originate from the 3p atomic orbital interaction in the triplet Si2 molecule. The measured isotopologue spectra of 29Si28Si and 30Si28Si indicate that the H3Σ?u - X3Σ?g transition system of 29Si28Si and 30Si28Si can be reasonably reproduced by the isotope mass-scaling rule. Spectroscopic parameters including the Franck-Condon factors, the Einstein coefficients, and the oscillator strengths, are also determined from the experimental results and the RKR calculations. The agreement between the experimentally measured and calculated dispersed fluorescence spectra indicates that the RKR calculations with the molecular constants determined in this work can accurately reproduce the diatomic potentials of both states. These molecular data providing a benchmark in high-level theoretical studies on Si2 and likely other small silicon clusters.