Transition, origin

Now the spectrum will show various transitions originating with state iih and ending on the various vibrational levels la of the lower electronic state. Equation (Bl.1.14) (or Bl.1.13) if we have to worry about variation of transition... 

The selection rule for vibronic states is then straightforward. It is obtained by exactly the same procedure as described above for the electronic selection rules. In particular, the lowest vibrational level of the ground electronic state of most stable polyatomic molecules will be totally synnnetric. Transitions originating in that vibronic level must go to an excited state vibronic level whose synnnetry is the same as one of the coordinates, v, y, or z. 

An interesting example occurs in the spectrum of the C2 molecule. The usual rule of absorption spectroscopy is that the transitions originate in the ground electronic state because only it has sufficient population. However, in C2 transitions were observed starting both from a fl state and from a jTstate, so it was not... 

The emission from copper is shown in Figure 2.66. The two prominent lines in the copper emission are termed the copper and K., lines. The transitions responsible are to the K shell, that with principal quantum number one, the 2s and 2p levels are referred to as the L shell, etc. The Greek letters indicate from where the transition originates the 2p Is transition gives the line and the 3p-> Is the line. Sometimes the line is split into a doublet as a result of exchange terms. 

As a result of the atomic nature of the core orbitals, the structure and width of the features in an X-ray emission spectrum reflect the density of states in the valence band from which the transition originates. Also as a result of the atomic nature of the core orbitals, the selection rules governing the X-ray emission are those appropriate to atomic spectroscopy, more especially the orbital angular momentum selection rule A1 = + 1. Thus, transitions to the Is band are only allowed from bands corresponding to the p orbitals. 

Fig. 7. Photothermal conductivity of n-type ultra-pure germanium, showing some hydrogen-oxygen donor and phosphorus transitions. In (b) the subscripts 1,2, and 3 of the D(H,0) symbol stand for transitions originating in the first, second and third shallower-lying ls-state. In (c) P stands for phosphorus.

As shown In Figure 5, azide bound to a single copper gives rise to one relatively Intense charge transfer absorption band. In analogy to peroxide, this transition originates from the level the... 

The forced electric dipole mechanism was treated in detail for the first time by Judd (1962) through the powerful technique of irreducible tensor operators. Two years later it was proposed by Jorgensen and Judd (1964) that an additional mechanism of 4/-4/ transitions, originally referred to as the pseudo-quadrupolar mechanism due to inhomogeneities of the dielectric constant, could be as operative as, or, for some transitions, even more relevant than, the forced electric dipole one. 

Welsh suggested correctly that similar transitions take place even if the molecular pair is not bound. The energy of relative motion of the pair is a continuum. Its width is of the order of the thermal energy, Efree 3kT/2. Radiative transitions between free states occur (marked free-free in the figure) which are quite diffuse, reflecting the short lifetime of the supermolecule. In dense gases, such diffuse collision-induced transitions are often found at the various rotovibrational transition frequencies, or at sums or differences of these, even if these are dipole forbidden in the individual molecules. The dipole that interacts with the radiation field arises primarily by polarization of the collisional partner in the quadrupole field of one molecule the free-free and bound-bound transitions originate from the same basic induction mechanism. 

Since the absorption spectra are diffuse over the entire spectral region, no assignments of transitions have been made from the analyses of the spectra. Hay and Goddard (449) have recently assigned the Hartley bands to a transition (origin at 3515 A) and the Chappuis bands to... 

Chang [621] studied the fluorescence characteristics Eu3+ doped Y2O3 crystals and claimed to have observed transitions originating from the 5Z>2 level of Eu3+ in addition to the prominent 5Z>0 - -7F2 transition (r = 870 psec) at 6115 A (16350 cm-1). Incorporation of other rare earth ions as codopents in Y2O3 Eu3+ crystals produced [622] pronounced effects on the fluorescence intensity and decay time of the >o 7F2... 

Such an effect of small molecule antiplasticiser is not specific to BPA-PC. It seems to occur with most polymers undergoing a transition originating from motions in the main chain. In the present paper, the effects of antiplasticisers on the f3 transition of poly(ethylene tere-phthalate) and epoxy networks are analysed in Sects. 4 and 7, respectively. 

In order to address this question we have considered the simpler case of two-photon bound-bound transitions originating from the ground state of... 

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