9914714241

VoI. X (1950)	Acta Physica Polonica	Fasc. 1—2
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INFLUENCE OF TORSIONAL VIBRATIONS OF LUMINES-CENT MOLECULES ON THE FUNDAMENTAL POLARI-Z ATI ON OF PHOTOLUMINESCENCE OF SOLUTIONS

By Alexander JABŁOŃSKI, Physios Department, Nicholas Copernicus

Uniyersity, Toruń.

(received June 15), 1949}

The obserred values oi fundanicntal polarization are always smaller tli a u thosc to bu expecte<l on the grountl of theoretical consideralions. This fact can bo esplained (at least partia Iły) by the influence of torsional vibrations of fluorescent molecules on the ratę of polarization of photol u mi uescence. Some conclusions eon be drawn from the diffcrcnce between theoretical and experiir.ental volues of thu polarization. This noto contains soiuu provi$ionnl results of theoretical investigation. A fuller report is mtc-nded to be published shortly.

According to Pauling (1030} and Stern (1031) the molecules (and parts of molecules) in many erystals can rotate if the temperaturę of the crystal is sufficicncly high. Ab Iow temperatures the molecules carry out smali oscillations (torsional vibrations) about their equi-librium orientations. The cnergy levels and the eorresponding eigen-functions approaeh in the case of diatomic molecules to lhose of a two dimensional oscillator. Tlie case of polyatomic molecules (three firnie Principal moments of inertia) was studied by Mrs W. Hanus (to bo published shortly). In the lnst case the levels and eigenfunetions of the lowest torsional yibration States are very nearly those of a three-dimcnsional harmonie oscillator. Thus molecules in erystals must possess an amount of torsional yibration energy even in their lowest State („zero point energy“).

Therc is no doubt thab similar torsional wibrations are canied out by luminescent molecules in solid (vitreous) or verv yfscous Solutions. Thcso vibratior.s (and sometimes also somo of the normal intemal Tibrations of molecules) must cause a partial depolarization of photo-luminescence. Since this cause persists down to the lowest temperatures (zero point energy!) it cannot be thoroughly eliminated by choosing suitable experimenta! conditions^l. Hence, the explanation of the faet

¹ In contradistinction to the two other thus fur kuown causes, i. e. to the Brownian rntntion of luminescent molecules and the transferenee of the exeitntion energy from one moleeulc to another.

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