Linear absorption spectrum

SubstiPitmg into equation (A 1.6.110) we find that the linear absorption spectrum is given by... 

Figure 4-2. INDO/SCI-siuiulaled linear absorption spectrum of the eleven-ring PPV oligomer. The vertical lines represent the oscillator strength of the transitions that are described the site labeling used tor the wavcluiiclion analyses is shown on lop.

To model the experimental data we used a global-fit procedure to simulate EPS, integrated TG, heterodyne-detected TG, and the linear absorption spectrum simultaneously. The pulse shape and phase were explicitly taken into account, which is of paramount importance for the adequate description of the experimental data. We applied a stochastic modulation model with a bi-exponential frequency fluctuation correlation function of the following form ... 

Fig. 2 (a) Linear absorption spectrum obtained on a 540 /rg/ml of GFPuv solution in a 1 mm thick cuvette (solid line) compared to that of GFPwt (dotted line) (data of ref [3]). (b) Multi-level schematic representation of the GFP emission mechanism [3]. 

In order to picture the underlying principles of nonlinear 2D-IR spectra, a model calculation of an idealized system consisting of two coupled vibrators is shown in Fig. 14b together with their linear absorption spectrum (Fig. 14a). The frequencies of these transitions were chosen as 1615 cm-1 and 1650 cm-1, the anharmonicity A = 16 cm-1, and the coupling fin = 7 cm-1. We used a homogeneous dephasing rate of T2 =... 

Figure 17 Cuts through the 2D-IR pump probe spectra shown in Fig. 16b and c along the direction of the probe axes for selected pump frequencies which were chosen to match the peaks in the linear absorption spectrum (squares 1648 cm-1 circles 1620 cru 1 triangles 1610 cm-1 diamonds 1584 cm-1). The frequency positions of the pump pulses are marked by the vertical dotted lines. (From Ref. 42.)...

As already mentioned, the poling held orients the molecule dipole moment in its direction, which (at least in situations depicted in Figs. 21 and 22) is usually perpendicular to the thin him surface. As the poled chromophores are strongly anisotropic, such a change of the orientation of dipole moments maybe well monitored by the observation of the thin him optical absorption spectrum [150, 151). Figure 25 shows the temporal variation of the optical absorption spectrum of a side-chain PMMA-DR 1 polymer. Two observations may be made from the temporal behavior of the linear absorption spectrum as shown in Fig. 26 ... 

Fig. 26. Experimental geometry for measurement of the variation of linear absorption spectrum due to poling [151]...

In general, and for the nonlinear hyperpolarizabilities to be derived below, one introduces r, for the transition between states w) and ). In effect the imaginary term iT o/2 takes the place of ie in Eq. (42). The linear absorption spectrum, which corresponds to the imaginary part of Eq. (45), will be built from smeared out Dirac delta functions of Lorentzian shape, i.e. the frequency-integrated absorption will remain constant regardless of the value of the lifetime broadening. The real part of the polarizability is related to the refractive index n of the sample... 

Despite the discouraging performance of the SOS approach for the electronic contributions to properties of more extended systems, the SOS formulas are frequently used for reasons of interpretation. Strongly absorbing states in the linear absorption spectrum may be identified as main contributors to the linear and nonlinear response properties, and truncated SOS expressions can be formed with this consideration in mind. In certain cases, molecules may have a single strongly dominant one-photon transition, and so-called two-states-models (TSM) can then be applied. The two states in question are obviously the ground state 0) and the Intense excited state /). 

The drastical enhancement of the TPA cross section in the presence of the solvent for the two-photon polymerization initiator [4-trans-[p-(N,N-Di- -butylamino)-p-stilbenyl vinyl piridinc (DBASVP) has been illustrated in a recent work by Wong et al. [112]. The DBASVP is the typical D-tt-A molecule exhibiting the positive solvatochromism (scheme 7). Hence, the lowest excited state of the DBASVP molecule has been found to be a CT state, which completely dominates the linear absorption spectrum. Wong et al. have combined the time-dependent density functional theory and the polarized continuum model (PCM) to evaluate the solvatochromic shift, TPA cross-section, and oxidation potential of the DBASVP molecule in different solutions. 

The existence of even parity states lying above the have been identified by two-photon absorption (TPA), two-photon fluorescence excitation [31], and electroabsorption (EA) spectroscopy. We measured the TPA spectrum of DOO-PPV by Z-scan [32] showing both the real and imaginary components of Figure 7-13 compares the linear absorption spectrum of DOO-PPV to the spectra of the real and imaginary molecular second hyperpolarizability. The imaginary component, y", is proportional to the TPA coefficient a2, while the real component, y, corresponds to the non-linear dispersion, 2- The y" spectrum shows a clear peak at % 3.2,5 eV, 0.5 eV above the peak of the l.B absorption band, and a shoulder at se3.5 eV, which may correspond to a second TPA band. The y spectrum clearly indicates dispersion near the two y" peaks, as expected from Kra-mers-Kronig analysis, and permits us to identify two distinct TPA bands. 

For the linear absorption spectrum, the system evolves in a coherence between the ground and one-exciton states after the interaction with the first pulse. Exciton relaxation occurs during the coherence period and influences the... 

By forming ion-rare gas atom (Rg) complexes, the dissociation threshold of the system is lowered, generally below the photon energy and these predissociation spectra directly reflect the linear absorption spectrum. This technique has also been used to great effect in anion spectroscopy experiments [13]. The multiphoton dissociation approach remains attractive for systems in which the perturbation of the messenger atom carmot be neglected, or in instruments where rare gas attachment is difficult. 

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