Location of the first excited states of fluorinated ethers, E143a (CH 3OCF 3), E134 (CHF 2OCHF 2), and E125 (CHF 2OCF 3)

The first excited states for dimethyl ether, E143a (CH ₃OCF ₃), E134 (CHF ₂OCHF ₂), and E125 (CHF ₂OCF ₃) have been located using the state-averaged CASSCF method. The first excited states have been found to lie at 185, 138, 122, and 114 nm for dimethyl ether, E143a, E134 and E125, respectively. The value for dimethyl ether is in good agreement with literature values. The effect of fluorinating dimethyl ether to form E143a is to blue shift the position of the first excited state by over 40 nm. These results are consistent with the methanol system, which sees an analogous shift of approximately 40 nm as methanol is fluorinated to form CF ₃OH. Implications for the photolysis of these fluorinated ethers in the atmosphere is discussed.