Transition coupling

Clebsch-Gordan coefficients coupling ground and excited levels that = transitions coupled by linearly... 

In the theory of deuteron spin-lattice relaxation we apply a simple model to describe the relaxation of the magnetizations T and (A+E), for symmetry species of four coupled deuterons in CD4 free rotators. Expressions are derived for their direct relaxation rate via the intra and external quadrupole couplings. The jump motion between the equilibrium positions averages the relaxation rate within the same symmetry species. Spin conversion transitions couple the relaxation of T and (A+E). This mixing is included in the calculations by reapplying the simple model under somewhat different conditions. The results compare favorably with the experimental data for the zeolites HY, NaA and NaMordenite [6] and NaY presented here. Incoherent tunnelling is believed to dominate the relaxation process at lowest temperatures as soon as CD4 molecules become localized. 

However, discussion of this type is very speculative and one can readily develop theories for the few facts known. It is important that the crystal spectrum should be more closely studied to determine at least the symmetry of the field. That the solid state band is polarized along the z-direction means that, whatever the symmetry, the excited state (the ground state is fully symmetric) must be represented in the same way as z, i.e., Blu in or Aiu in Dih- This can arise directly if the transition is to the jvorbital, but can also arise from symmetrical transitions coupled to unsymmetrical vibrations. When this transition has been given an assignment, it will then be somewhat, simpler to consider the causes of its movement with variations in the metal-metal distance. 

The electronic absorption spectra of complex molecules at elevated temperatures in condensed matter are generally very broad and virtually featureless. In contrast, vibrational spectra of complex molecules, even in room-temperature liquids, can display sharp, well-defined peaks, many of which can be assigned to specific vibrational modes. The inverse of the line width sets a time scale for the dynamics associated with a transition. The relatively narrow line widths associated with many vibrational transitions make it possible to use pulse durations with correspondingly narrow bandwidths to extract information. For a vibration with sufficiently large anharmonicity or a sufficiently narrow absorption line, the system behaves as a two-level transition coupled to its environment. In this respect, time domain vibrational spectroscopy of internal molecular modes is more akin to NMR than to electronic spectroscopy. The potential has already been demonstrated, as described in some of the chapters in this book, to perform pulse sequences that are, in many respects, analogous to those used in NMR. Commercial equipment is available that can produce the necessary infrared (IR) pulses for such experiments, and the equipment is rapidly becoming less expensive, more compact, and more reliable. It is possible, even likely, that coherent IR pulse-sequence vibrational spectrometers will... 

Probably the most interesting feature of SCLCPs is their ability to freeze an anisotropic alignment below the glass transition, coupled with the fluidity of the mesophase [32]. This alignment can be attained by electric, magnetic or mechanical fields. 

Kimura T., Kumai R., Tokura Y., Li J.Q. and Matsui Y., Successive Structural Transition Coupled with Magnetotransport Properties in LaSr2Mn207, Phys. Rev.B, 58 (1998) pp.l 1081-11084. 

In the gas phase, the vibrational transitions couple with the rotational ones, giving rise to rotovihrational spectra. The different rotovibrational contours depend on the symmetry of the vibration in relation to the symmetry of the molecule, and on the resolution of the rotational components. In some cases, the energy of the pure vibrational transition corresponds to the minimum of the absorption band ... 

One of the key aspects concerning the excitation mechanism is which electronic transitions couple to the coherent nudear motions. As for the surface adsorbate excitations, there are two extreme cases for the electronic transition which leads to surface dynamics. One is the adsorbate localized excitation and the other is the substrate-mediated excitation. In many cases, investigating the reaction yield by changing the characters of inddent photons (polarization, energy, etc.) helps to confirm which mechanism operates. If a substrate-mediated process dominates, the reaction yield follows the features of bulk absorption, whereas a deviation from the bulk absorption property would be observed for the surface localized excitations. 

The /z-m mechanism is similar in concept, but assumes interaction of a transition dipole within one group with a transition quadrupole (magnetic moment) within the other group. It is much more difficult to recognize and to apply, n-n transitions coupling with n-n transition in oligopeptide molecules depict such a situation [81, 82]. 

Pump transition Coupled transition (v = 1 excited state) ... 

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