Comparison of high and zero magnetic field values of non radiative triplet-triplet annihilation rate constants in crystalline anthracene

Experimental indications are given which show that the non-radiative triplet-triplet annihilation rate constant (ARC) gamma nr in anthracene has the same value at high (3 kOe) and zero magnetic field. From the anisotropy of the negative magnetic field effect on the electron-hole recombination emitted light, it is also shown that gamma nr/gamma r = 1.5 +/- 0.3, where gamma r is the radiative ARC. Electron-hole recombination, triplet and singlet creation yields in the recombination process are also identical at high and zero fields.