โ Scribed by C.R. Chen; J.A. Mucha; D.W. Pratt
No coin nor oath required. For personal study only.
Absorption and stimulated emission of microwaves has been observed in the 3 cm MODR spectrum of the photoexcited triplet state of symmetric tetrachlorobcnzene (s-TCR) in a duxnc host crystal at liquid helium temperatures. Studies of the rebtk intensities of the "A?us + cl" transitions as a function of temperature, with the magnetic field directed along molecular fine structure ascs, have been used to determine the absolute signs of the zero-field (ZF) parameters. Combining these results with those from experiments done in zero field, it is found that D = +0.1518 and E = +0.02908 cm-'. The signs of the ZF parameters in the rr ,r* triplet stites of aromatic molecules arc discussed, and it is shown that the sign of E in s-TCB and other substituted bcnzenes such as pdichlorobenzene can be prrtiicted using simple molecular orbital considerations.
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