Location of the first excited states of fluorinated ethers, E143a (CH3OCF3), E134 (CHF2OCHF2), and E125 (CHF(2)OCF3)

The first excited states for dimethyl ether, E143a (CH3OCF3), E134 (CHF2OCH F2), and E125 (CHF2OCF3) have been located using the state-averaged CASSCF method. The first excited states have been found to lie at 185, 138, 122, a nd 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 wit h the methanol system, which sees an analogous shift of approximately 40 nm as methanol is fluorinated to form CF3OH. Implications for the photolysis of these fluorinated ethers in the atmosphere is discussed. (C) 1999 Elsevi er Science B.V. All rights reserved.