Vibronic resonance

In the case that an isolated vibronic resonance interacts with the uncoupled (or elastic ) continuum of Eq. (48), Eq. (43) simplifies to... 

In the limit of an isolated vibronic resonance are real, decay of the resonances arises only from interaction with the continuum, Eq. (52) reduces to... 

When the gap is large, the sketch in Fig. 9 shows that a second channel will open when there is a vibrational resonance - that is, when eV = ho, with o one of the vibrational frequencies of the molecule. This is vibronic resonance, and energy will transfer from the momentum of the tunneling electrons into the vibrations of the molecule. The interaction is quite weak (because the tunneling time is so short) ... 

This is a very unique situation for superconductivity, since in the previous experience inhomogeneity is almost always harmful to superconductivity. Why is the superconductivity in the cuprates so different While further research is clearly required to answer this puzzle, one possibility is that the spatial confinement produces the vibronic resonant state of phonon and charge that enhances HTSC [15,23], The benefit of spatial confinement on HTSC has been strongly advocated for some time by Phillips with the idea of filamental superconductivity [24] and more recently by Bianconi [25] as the shape resonance effect. In both cases the effect arises due to the enhancement of the local density of states (DOS). An additional, and possibly more central, effect of confinement is to reduce the group velocity of electrons and bring it comparable to the phonon velocity, thus... 

An alternative explanation can be given in terms of a vibronic resonance effect, i.e., population transfer occurs due to the fact that the high-frequency subspace is tuned into resonance as a function of the low-frequency motions [88,96], This is very similar to resonant vibration-vibration coupling in liquids [95] where the transfer of vibrational excitation between solute species is mediated by low-frequency solvent modes. 

If the mechanical degrees of freedom are coupled strongly to the environment (dissipative vibron), then the dissipation of molecular vibrations is determined by the environment. However, if the coupling of vibrations to the leads is weak, we should consider the case when the vibrations are excited by the current flowing through a molecule, and the dissipation of vibrations is also determined essentially by the coupling to the electrons. Here, we show that the effects of vibron emission and vibronic instability are important especially in the case of electron-vibron resonance. 

This discussion has shown the importance of the two-particle states in critically modulating the lineshape of the vibronic absorption, which appears very broad, generally nonlorentzian, and with shifts in the vibronic resonances... 

The next structures are 3b at 25 665 cm"1 and 3a at 25 672cm-1, which are broad bumps attributed to vibronic resonances greatly diluted in the two-... 

We refer here to vibronic resonance Raman spectroscopy. 

Albrecht A C, Clark R J H, Oprescu D, Owens S J R and Svensen C 1994 Overtone resonance Raman scattering beyond the Condon approximation transform theory and vibronic properties J. Chem. Phys. 101 1890-903... 

Page J B 1991 Many-body problem to the theory of resonance Raman scattering by vibronic systems Top. Appi. Phys. 116 17-72... 

Ohung Y 0 and Ziegler L D 1988 The vibronic theory of resonance hyper-Raman scattering J. Chem. Phys. 88 7287-94... 

Figure Bl.6.11 Electron transmission spectrum of 1,3-cyclohexadiene presented as the derivative of transmitted electron current as a fiinction of the incident electron energy [17]. The prominent resonances correspond to electron capture into the two unoccupied, antibonding a -orbitals. The negative ion state is sufficiently long lived that discrete vibronic components can be resolved.

Wang C, Mohney B K, Williams R, Hupp J T and Walker G C 1998 Solvent control of vibronic coupling upon intervalence charge transfer excitation of (NC)gFeCNRu(NH3)g- as revealed by resonance Raman and near-infrared absorption spectroscopies J. Am. Chem. Soc. 120 5848-9... 

The easiest method for creating many vibrational excitations is to use convenient pulsed visible or near-UV lasers to pump electronic transitions of molecules which undergo fast nonradiative processes such as internal conversion (e.g. porjDhyrin [64, 65] or near-IR dyes [66, 62, 68 and 62]), photoisomerization (e.g. stilbene [12] or photodissociation (e.g. Hgl2 [8]). Creating a specific vibrational excitation D in a controlled way requires more finesse. The easiest method is to use visible or near-UV pulses to resonantly pump a vibronic transition (e.g. 

As discussed in preceding sections, FI and have nuclear spin 5, which may have drastic consequences on the vibrational spectra of the corresponding trimeric species. In fact, the nuclear spin functions can only have A, (quartet state) and E (doublet) symmetries. Since the total wave function must be antisymmetric, Ai rovibronic states are therefore not allowed. Thus, for 7 = 0, only resonance states of A2 and E symmetries exist, with calculated states of Ai symmetry being purely mathematical states. Similarly, only -symmetric pseudobound states are allowed for 7 = 0. Indeed, even when vibronic coupling is taken into account, only A and E vibronic states have physical significance. Table XVII-XIX summarize the symmetry properties of the wave functions for H3 and its isotopomers. 

We consider a general dissipative environment, using a three-manifold model, consisting of an initial ( ), a resonant ( r ), and a final ( / ) manifold to describe the system. One specific example of interest is an interface system, where the initial states are the occupied states of a metal or a semiconductor, the intermediate (resonance) states are unoccupied surface states, and the final (product) states are free electron states above the photoemission threshold. Another example is gas cell atomic or molecular problems, where the initial, resonant, and final manifolds represent vibronic manifolds of the ground, an excited, and an ionic electronic state, respectively. 

It is relatively easy to decide which vibronic bands have a common origin. This is accomplished by observing the phosphorescence intensity change of each band upon microwave saturation at a frequency that corresponds to transitions between rz and tx. This is known as phosphorescence-microwave double resonance (PMDR) spectroscopy. These frequencies for 2,3-dichloroquinoxaline are given in Table 6.3. 

Nonradiative transfer of excitation energy requires some interaction between donor and acceptor molecules and occurs if the emission spectrum of the donor overlaps the absorption spectrum of the acceptor, so that several vibronic transitions in the donor must have practically the same energy as the corresponding transitions in the acceptor. Such transitions are coupled, i.e., they are in resonance, and that is why the term resonance energy transfer (RET) or electronic energy transfer (EET) are often used. 

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