Dipolar excitation

W. R. Garrett, Phys. Rev. A, 3, 961-972 (1971). Critical Binding of an Electron to a Rota-tionally Excited Dipolar System. 

ColvinVL, Cunningham K L and Alivisatos A P 1994 Electric field modulation studies of optical absorption in CdSe nanocrystals dipolar character of the excited state J. Chem. Phys. 101 7122... 

For conjugated carbonyl compounds, such as a,) -enones, the orbital diagram would be similar, except for the recognition that the HOMO of the ground state is ij/2 of the enone system, rather than the oxygen lone-pair orbital. The excited states can sometimes be usefully represented as dipolar or diradical intermediates ... 

The rhodium-catalyzed tandem carbonyl ylide formation/l,3-dipolar cycloaddition is an exciting new area that has evolved during the past 3 years and high se-lectivities of >90% ee was obtained for both intra- and intermolecular reactions with low loadings of the chiral catalyst. 

In addition to sample rotation, a particular solid state NMR experiment is further characterized by the pulse sequence used. As in solution NMR, a multitude of such sequences exist for solids many exploit through-space dipolar couplings for either signal enhancement, spectral assignment, interauclear distance determination or full correlation of the spectra of different nuclei. The most commonly applied solid state NMR experiments are concerned with the measurement of spectra in which intensities relate to the numbers of spins in different environments and the resonance frequencies are dominated by isotropic chemical shifts, much like NMR spectra of solutions. Even so, there is considerable room for useful elaboration the observed signal may be obtained by direct excitation, cross polarization from other nuclei or other means, and irradiation may be applied during observation or in echo periods prior to... 

By omitting time-dependent terms, as in the preceding paragraph, the liP ) function may be read as the sum of the unperturbed wavefunction ) and a term which is the product of this function by a linear combination of the electronic coordinates, i.e. the Kirkwood s j) function. Thus, the (r) dipolar factor ensures gauge-invariance. But the role of the dipolar factor g f) in this mixed method is essential on the following point its contribution in the a computation occurs in a complementary (and sometimes preponderant) way to that calculated only from the n) excited states, the number of which is unavoidably limited by the computation limits. But before discussing their number, we have to comment the description of these states. 

We have first been concerned with the computational point of view. Through the calculation of the dynamic polarizability of CO, we have developed a method based on the conventional SCF-Cl method, using the variational- perturbation techniques the first-order wavefunction includes two parts (i) the traditional one, developed over the excited states and (ii) additional terms obtained by multiplying the zeroth—order function by a polynomial of first-order in the electronic coordinates. This dipolar... 

In this Section we want to present one of the fingerprints of noble-metal cluster formation, that is the development of a well-defined absorption band in the visible or near UV spectrum which is called the surface plasma resonance (SPR) absorption. SPR is typical of s-type metals like noble and alkali metals and it is due to a collective excitation of the delocalized conduction electrons confined within the cluster volume [15]. The theory developed by G. Mie in 1908 [22], for spherical non-interacting nanoparticles of radius R embedded in a non-absorbing medium with dielectric constant s i (i.e. with a refractive index n = Sm ) gives the extinction cross-section a(o),R) in the dipolar approximation as ... 

The energy available from the anthracene triplet (42 kcal/mole) is sufficient to produce either of these states. The singlet excited molecule subsequently attacks a ground state anthracene to produce the observed endoperoxide. The 1Aff state is believed to be responsible for the addition to anthracene to form the endoperoxide since it closely resembles a diradical species, while the 1Ss+ state more closely resembles a dipolar ion. 

The first two terms in (5) are called D-terms or dipolar terms, which are nonzero only if Ape =/= 0. The two-photon resonance denominator, ( leg — 2hco), indicates that an electron is excited into the lower excited state e. If we consider a near resonance condition hco = %imaginary part of the D-terms can be written in SI units as ... 

Fig. 5 Combinatorial synthesis of triazolylcoumarin library using Cu(I)-catalyzed 1,3-dipolar cycloaddition reaction. Each letter represents the relative fluorescence intensities H High, M Middle, L Low. The excitation and emission spectra were recorded in DMF. Reproduced with permission from reference [45]... 

Chou PT, Huang CH, Pu SC et al (2004) Tuning excited-state charge/proton transfer coupled reaction via the dipolar functionality. J Phys Chem A 108 6452-6454... 

Chou PT, Pu SC, Cheng YM et al (2005) Femtosecond dynamics on excited-state proton/ charge-transfer reaction in 4 -N, N-diethylamino-3-hydroxyflavone. The role of dipolar vectors in constructing a rational mechanism. J Phys Chem A 109 3777-3787... 

Fig. 1 Mesomeric structures of a para-substituted benzene intramolecular charge transfer (ICT) complex in the ground state and in the dipolar excited state...

The fact that dynamic 13C polarization is only possible through the indirect way via tire 1H spins suggests the mechanism of polarization transfer. Since the polarization transfer between the electrons and nuclei are driven by the dipolar interactions between them, and the fraction of the guest triplet molecules was small, it would be natural to assume that the polarization of the electron spins in the photo-excited triplet state is given to those H spins which happen to be close to the electron spins, and then the 1H polarization would be transported away over the whole volume of the sample by spin diffusion among the 1H spins. 

Other exciting applications involved using parallel tempering in connection with available experimental data. For example, Falcioni and Deem [57] used X-ray data to refine structures of zeolites, and Haliloglu et al. [58] refined NMR structural data for proteins (in particular using residual dipolar coupling constraints). 

The results from EFISHG or HRS experiments can be corrected for resonance enhancement by using a simple theoretical two-state model (TSM, Equations (3) and (4)),35,36 which is reasonably valid for dipolar molecules in which f3 is primarily associated with a single ICT excitation ... 

Before reviewing existing examples, a very brief explanation on the mechanisms of decoherence for molecular spin qubits is necessary more details are available elsewhere [67]. Broadly speaking, the three decoherence sources for these systems are spin bath decoherence, oscillator bath decoherence and pairwise dipolar decoherence, and can be regulated by a combination of temperature, magnetic field and chemical design of the system [70]. The spin bath mainly consists of nuclear spins, but in general it also includes any localized excitations that can couple to the... 

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