Phosphorescence lifetimes have been measured for acetone and acetone-leO in EPA glass and in the ~ystalUne state both at 77Β°K. The lifetime of acetone-180 was found to be about 10% longer than that of normal acetone. These results are discussed in terms of theories of electronic relaxation.
The fact that deuterium substitution increases the phosphorescence lifetimes of a large number of aromatic hydrocarbons [ 1], and other organic compounds [2], including acetone [3,4], is well known. However, to our knowledge, the only previous at: tempt to observe an isotope effect with respect to substitution of heavier atoms was the work of Martin and Kalantar [51 on 13C substituted benzene. These authors measured the phosphorescence lifetime of t 3 CC 5 H6 (52.8% isotopic purity) in several glassy solvents at 77Β°K and obtained lifetimes which agreed with those measured for C6H 6 within about I%. Since their estimated experimental uncertainty was also about 1%, one concludes that 13C isotope effects in the triplet state relaxation of benzene are certainly very small, and perhaps, totally absent.
In the present note we report results of phosphorescence measurements on acetone-180.
Fisher Spectranalyzed acetone was dried over molecular sieves, distNed throu~ a packed column at atmospheric pressure and then outgassed and vacuum distilled. Acetone-180, obtained from Miles-Yeda (manufacturer reports 90.8 atom % 180,0.41 atom % 170, as determined mass spectrometrically), was outgassed and vacuum distilled. Measurements iSh crystalline materials were made in 3ram quartz tubes. Measurements on 0.1 M acetone in EPA (MCB Spectroquality)