Dressed molecules

Atabek, O., Lefebvre, R., and Jacon, M. (1980a). Continuum resonance Raman scattering of light by diatomic molecules. I. The role of radiative crossings between the potentials of the dressed molecule, J. Chem. Phys. 72, 2670-2682. 

As a result of the interaction between the molecule and the boson field, the bare molecule becomes dressed with a cloud of boson particles in the language of Sect. 2 the dressed molecule is an elementary excitation in the many-body system of molecules and boson particles. The number density of dressing boson particles is given by... 

In other studies, Davies14 15) and Pfeifer11,12) (see below) have described models with the property that T = °o because the dressed molecule involves a cloud of soft (long... 

In a subsequent paper, Munn [98] showed that the frequency-dependent local-field tensors accounted for the shift of the poles of the linear and nonlinear susceptibilities from the isolated molecular excitation frequencies to the exciton frequencies. The treatment also described the Davydov splitting of the exciton frequencies for situations where there is more than one molecule per unit cell as weU as the band character or wave-vector dependence of these collective excitations. In particular, the direct and cascading contributions to x contained terms with poles at the molecular excitation energies, but they canceled exactly. Combining both terms is therefore a prerequisite to obtaining the correct pole structure of the macroscopic third-order susceptibility. Munn also demonstrated that this local field approach can be combined with the properties of the effective or dressed molecule and can be extended to electric quadrupole and magnetic dipole nonlinear responses [96]. 

Dressed molecule picture and laser-induced resonances 61... 

Hamiltonian in an extended space, the direct product of the usual molecular Hilbert space, and the space of periodic functions of f e [0,T]. This extension of the Hilbert space can be made somewhat more transparent by introducing a new time-like variable, to be distinguished from the actual time variable t. This new time variable can be defined through the arbitrary phase of the continuous (periodic) field, as done in Ref. [28, 29]. A variant of the idea is found in the (f, t ) method developed by Peskin and Moiseyev [30] and applied to the photodissociation of HJ [31, 32]. We will continue with the more traditional and simpler formulation of Floquet theory here, as this is sufficient to bring out ideas of laser-induced resonances in the dressed molecule picture. 

Some surfactants are used as emulsifiers in processed foods such as bottled salad dressing. An emulsifier causes normally incompatible liquids such as the oil and water in salad dressing to disperse in each other, by forming molecular connections between the liquids. The hydrophobic tails of emulsifier molecules Interact with oil molecules, while the hydrophilic heads on the emulsifier molecules interact with water molecules. 

The belief that computational chemists obtain molecular structures by solving Schrodinger s equation is often dressed up in so much jargon that the essential arguments are obscured. The general basis of the belief may be examined by considering the simplest possible molecule as a test case5. 

The results for N2 are summarized in Table 3. The bond is streched from 2.15 a.u. up to 3.00 a.u. Opposite to the previous molecules, even at the equilibrium geometry CCSD does not perform as well as the other approaches. For the [6e/6o] active space, it differs from FCI by 12.9 mHa, while CAS-SDCI does it by 8.3 mHa, (SCf CAS-SDCI by 3.9 mHa and ec-CCSD by 2.0 mHa or 1.8 mHa, depending on the external correcting source. Again, one may observe that the minimal dressing of CAS-SDCI not only makes it size-extensive, but also improves the absolute value of the yielded energy. 

However, this is in general a quite impractical method, as it requires the iterative series of dress-then-diagonalize steps to get convergence for each individual state. Moreover, even if no particular numerical problems arise in the case of states that are not dominated by one particular excitation, the method does not seem to be well-adapted from a formal point of view to such cases because they do not satisty the condition stated in eq. (2). Notwithstanding, this procedure can be practical for the calculation of outer-valence ionization potentials of closed-shell molecules. In such cases, one must to deal with the doublet states of the cation that are well dominated by a unique Koopmans determinant. 

The simplest (SC) SDCl calculations give a very important improvement over the Koopman s IPs for the same basis set. It should not be expected that a Cl takes into account properly the repolarization effects of the MOs of the cation relative to the neutral molecule. However, the MAE is reduced from 1.3 eV (KT) to 0.23 (SDCl) or 0.18 eV ((SC) SDCl). A further improvement ofthe results can be obtained with CAS-SDCI. The calculations have been performed in the C2v point symmetry group, so that we indicate the active spaces as (nj U2n3n4) corresponding respectively to the irreducible representations (ai bi b2 a2). The CAS for the ground state of CO was 8 electrons in (2220). For the 5o and 4o cations, the CAS was 7 electrons in (2220) also, but for the second excited state of the same symmetry (4o cation), the second vector was dressed. The n cation gave good results with a smaller CAS of 3 electrons in (0220). The MAE... 

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