SINGLET EXCITATION-ENERGY MIGRATION IN THE GLASSY AND SINGLE CRYSTALLINE STATES OF 1,3-DIPHENYL-5-(P-CHLOROPHENYL)-2-PYRAZOLINE

Comparative studies were made of the singlet excitation energy migration of 1,3-diphenyl-5-(p-chlorophenyl)-2-pyrazoline between the glassy and single crystalline states at near room temperature. The rate parameter for the singlet excitation energy migration, i. e. , frequency of excitation hopping, was determined from the fluorescence quenching by the guest molecule, dimethylterephthalate, the quenching process being the migration controlled charge-transfer. The results are discussed in terms of both kinetic and random migration models. The results show that the single excitation energy migrates over 523 plus or minus 9 molecules in the glassy state and (3. 71 plus or minus 0. 06) multiplied by 10**5 molecules in the single crystalline state at 10 degree C within its lifetime which was found to be almost the same in both states. The rate parameter for the migration is slightly temperature dependent, the apparent activation energy being similar 0. 052 ev in the glassy state and similar 0. 012 ev in the single crystalline state. It is indicated that the difference of the two or three orders of magnitude in the efficiency of migration between the disordered and ordered system is mainly due to the difference of the preexponential frequency factor rather than of the activation energy.