TEMPERATURE-DEPENDENT ULTRAVIOLET-ABSORPTION CROSS-SECTIONS OF 1,3-BUTADIENE AND BUTADIYNE

The temperature dependence of the ultraviolet absorption cross section s of 1,3-butadiene, from 160 to 240 nm, and butadiyne (diacetylene) fr om 160 to 260 nm have been measured, in the gas phase, for temperature s ranging from about 220 to 330 K. The absorption spectrum of 1,3-buta diene shows several sharp absorption features between 160 and 190 nm a nd strong diffuse bands between 190 and 220 nm. The absorption cross s ections, at absorption peaks, increased significantly with decreasing temperature, particularly in the range 185 to 215 nm. At about 220 nm, a cross over point, the absorption cross section remained unchanged w ith temperature variations while at wavelengths greater than 220 nm th e cross section values decreased with decreasing temperature. A sharp absorption feature at 186.6 nm shows the most pronounced relative temp erature effect with an increase in the cross section from 42.55 X 10(- 18) to 78.70 X 10(-18) cm(2) for a temperature change of 333 to 218 K. The spectrum for butadiyne consists of a very strong absorption at 16 4.6 nm with a cross section of 4.40 X 10(-16) cm(2), at 295 K, followe d by the complex absorption features between about 200 to 250 nm. The cross section values at absorption peaks determined at low temperature s are significantly higher than those at higher temperatures.