Reactions of Photochemically Produced Hot Hydrogen Atoms. I. Photolysis of HI at 1849 Å

Spectroscopic evidence as to the primary processes caused by absorption of 1849-Å radiation by HI is evaluated and clarified as a basis for consideration of chemical reactions of the 3.6 and 2.6-eV H atoms which may be formed at this wavelength. The energetics of possible hot H reactions with HI which might raise φH2 above the value of unity observed at 2537 Å are evaluated. Experimental results are presented on the photolysis of HI by 1849-Å radiation at —78° and 25°C, showing that little or no enhancement of the yield by such hot processes occurs. Quantum yields of HI decomposition at 1849 Å of 0.5 or greater are found in HI–I2 systems where 90% of the radiation is absorbed by I2, indicating a high probability of photosensitized decomposition of HI by excited I2 molecules or of absorption of I2 fluorescence radiation by HI, or both.