Polarized Light Emission Research Articles

Lattice Relaxation and Time Resolved Polarization of Emission from Localized Electron with Level Crossing

The polarization of emitted light from a localized electron in a crystal is calculated on the basis of the theory of the time resolved emission including the lattice relaxation. A three level system composed of an s -like ground state, x - and y -like excited states is worked out as an example. The depolarization is found to occur around the time when the phonon wave packet passes the intersection of the two adiabatic potential energies of the excited states, and its probability conforms to the Landau-Zener formula under certain conditions.

Excitation of Hg(6 3P1) by low energy alkali ion impact: Optical polarization and cross sections for magnetic sublevels

Intensity and polarization of emitted light from collisions of ground state alkali ions and mercury atoms have been studied by a combined crossed-beam and optical technique. Both the intensity and polarization of the Hg(6 3P1→6 1S0)−253.7 nm line exhibit a pronounced structure as a function of ion energy in the investigated range (from apparent thresholds to 3 keV); in particular, the polarization fraction takes on in succession very large positive and negative values. From the emission cross sections for several transitions, after correction for cascade and anisotropy, absolute cross sections for the excitation process M++Hg(6 1S0) →M++Hg(6 3P1), where M+=Li+, Na+, and K+, have been obtained. Using emission and polarization data, cross sections for population of the magnetic sublevels, mj=0 and ‖mj‖=1, have also been obtained. These cross sections have apparent thresholds much larger than the endoergicities of the processes, but reach very high values (of the order of 10−16 cm2) in the investigated energy range; they also show a pronounced oscillatory structure. Although it appears that the primary excitation mechanism involves short-range repulsive forces, the final evolution of the collision system towards products is best depicted by reference to the adiabatic potential energy curves for the HgM+ molecules. In particular the prominent structure in the cross sections for the magnetic sublevels, which oscillate in antiphase, is discussed in terms of quantum mechanical phase interference between the quasimolecular terms dissociating to the 3P1 state of mercury.

A theoretical evaluation of the effect of photoselection on the measurement of the circular polarization of luminescence

The orientation of molecules excited by a beam of light is not isotropic as a rule. If rotatory Brownian motion is not fast during the lifetime of the excited state the polarization properties of the light emitted from the excited molecules will depend as a rule on the mode of photoselection of the molecules by the excitation beam. A general theoretical method is developed for proper weighting in the process of summing of the contributions of the various photoselected molecules to the emitted light when Brownian rotational motion is frozen. A formula is obtained for the calculation of the probabilities of emission of light of a specified polarization from the photoselected system. To use this formula average values of multiples of elements of the Euler matrix are to be evaluated first; the polarization properties of the emitted light are then obtained by insertion of the components of the electric and magnetic transition dipole moments characterizing the absorption and emission of light by the molecule under discussion. By use of this formula, the Perrin-Jablonski formula for the linear polarization of emitted light is derived in a simple fashion. It is shown that for asymmetric molecules the degree of circular polarization of the emitted light is affected by photoselection if the electric transition moments responsible for absorption and emission are not parallel. It is of much interest that under such circumstances the angle between the emitting electric and magnetic dipole moments can in principle be obtained.