Fluorescence Intensity Ratio of Sodium Doublet Observed in the Optical Dissociation of Sodium Iodide Vapor

The intensity ratio D₂/D₁ for the sodium doublet has been measured for radiation from excited sodium atoms which result from the optical dissociation of sodium iodide vapor by ultraviolet light in the 2082→2500 A region. With shorter wavelength ultraviolet light as exciting source, the D₂/D₁ ratio is 0.98 and increases to above 1.5 with longer exciting wavelengths. Addition of foreign gases cause the observed D₂/D₁ ratio to increase to 1.89 for large foreign gas pressure. Cross sections for the transfer of excited sodium atoms from the $3^2{P}_{\frac{3}{2}}$ to the 3²P_½ state and vice versa due to collisions with foreign molecules have been measured as they depend on the relative velocity between excited sodium atom and foreign molecule. The Doppler broadening of the separate D lines emitted in the atomic fluorescence of sodium iodide has been estimated from absorption measurements. Both lines show equal broadening within the experimental error of the observations. Measurements were made with a photomultiplier tube. The sodium doublet was resolved with a reflection grating monochromator.