Transition polar

Fig. 10.4 Experimental scheme for the 2D [ N. HJ-TROSY using single transition to single transition polarization transfer (box labeled ST2-PT). On the lines marked H and 15N, narrow and wide bars stand for nonselective 90° and 180° radio-frequency pulses, respectively. The delay t=2.7 ms (see text). The line marked PFG indicates the pulsed magnetic field gradients applied along the z-axis G, amplitude 30 G/cm, duration 1 ms G2, 40 G/cm, 1 ms G3, 40 G/cm, 1 ms ...

TRANSITION DIPOLE MOMENT TRANSITION POLARIZATION TRANSITION PROBABILITY FUNCTIONS TRANSITION STATE... 

Thus at least three Eu " centers take place in zircon, which have been characterized in Table 5.1 by the main transitions, polarizations and decay times of each emitted level. These centers may be reasonably connected with Zr + cation substitution within a tetragonal ZrSi04 structure with space group I4i/amd... 

Transition polarization The direction of the transition moment in the molecular framework. 

Key words Exciton, interband transition, polarization, band structure... 

In the two state model, where the entire elfect is attributed to the contribution of one nn transition polarized along the direction (z) of the ground state dipole, the hyperpolarizability becomes,... 

Due to the pairing theorem, the absorption spectra and transition polarization directions of two mutually paired alternant systems should be identical, as shown in Figure 2.25 for the radical anion and the radical cation of tetra-cene. Under the same conditions (i.e., = 0 if and v are nonneighbors),... 

The ratio C/D is given by g abKa - -t 6 ). When the Fe(III) ion has a four-fold axis of symmetry, then x = y, and Y, the rhombic distortion parameter, will be zero. The unpaired electron is equally shared between the da and dyz orbital and, as a consequence, a = 6. In this case C/D = 2/2, which is the maximum value it can have (59). However, in the limit of maximum rhombic distortion, x + y, the degeneracy of the da yz pair is lifted, and the electron becomes localized in one orbital, say, dyz. At the limit, one of the coefficients, say a, becomes zero. Hence the C term intensity and the MCD signal go to zero. However, because a - + b = - c, the dipole strength, D, remains unaffected. This argument shows that though the intensity of the absorption spectrum is unaffected by rhombic distortion at the Fe(III) ion, the MCD intensity is sensitive to variations in V. The exact dependence of the MCD C term intensity upon the rhombic distortion parameter V is shown in Fig. 11. In the limit that V = 0, the transition eg(d ) is equally X and y polarized. However, as V tends to infinity, the CT transition, say Oiu g(dyz) becomes purely y polarized. A one-dimensional transition has no MCD intensity because the absorption of circularly polarized radiation requires two transitions polarized perpendicular to the applied field. 

Our first use of crystal polarization was in hexamethylbenzene. It had all molecular planes parallel to one another and perpendicular to the main faces of a sublimed crystal. It was known that the lowest absorption system was polarized in the molecular plane, conforming with its assignment to a n-n transition. However in the next system of benzene at 200 nm, corresponding to the hexamethylbenzene system at 230 nm, the vapour phase spectrum had been assigned to a Rydberg transition polarized perpendicular to the molecular plane [210]. 

Veratric acid, irradiation of 1079 Vibrational modes, of phenol 34-44 Vibrational spectroscopy 367 Vibrational transitions, polarization directions of 368... 

In the vicinity of a dipole allowed degenerate transition, polarized perpendicular to the optical axis, instead of (4.77) we have... 

Consequently in the vicinity of an allowed transition, polarized perpendicular to the optical axis in a uniaxial crystal, with Coulomb interaction fully taken into account, for a given value of k we obtain not one, but two exciton states. This distinction from the case when the tensor ey is given by the relations (4.77), results from properties of states determined by the poles of ey. 

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