Ultraviolet Resonance Spectrum of the Iodine Molecule

The ultraviolet resonance spectrum of I2 observed in electric discharges in the region 1830–2370 A has been photographed at high resolution with a 21‐ft vacuum grating spectrograph, and a thorough and complete analysis of the data in this region is given. The five doublet resonance series are shown to be excited from five rotational levels of vibrational level v″=0 of the ground state of I2 to three vibrational levels (vn′,vn+0′,vn+4′) of an upper electronic state by a single iodine atomic line 1830.4 A. The rotational constants for the ground state of I2 may be represented: (1)v=0.03734−0.0001208 (v+12)+0.444×10−6(v+12)2−1.839×10−8(v+12)3−0.057×10−10(v+12)4(2)v=1.99×10−9+1.236×10−10(v+12). The ground‐state ΔG(v+12) values have been obtained from v″=0 up to the dissociation limit. A precise value of the dissociation energy of I2, has been found to be 12 452.5±1.5 cm—1 as against the previous value of 12439±8 cm—1.The potential energy curve of X 1Σg+ has been computed by using the Rydberg‐Klein‐Rees method...