Emission spectra simulations

Figure 15.7 Emission from a bound upper state (/ =40) to a repulsive lower state, with the resulting oscillatory continuum emission spectrum (simulated) the inset shows the related potential energy curves. Adapted from Tellinghuisen, Adv. Chem. Phys., 1985, 60 299, with permission of John Wiley Sons Ltd...

Abstract A formal derivation of the nuclear-ensemble method for absorption and emission spectrum simulations is presented. It includes discussions of the main approximations employed in the method and derivations of new features aiming at further developments. Additionally, a method for spectrum decomposition is proposed and implemented. The method is designed to provide absolute contributions of different classes of states (localized, diffuse, charge-transfer, delocalized) to each spectral band. The methods for spectrum simulation and decomposition are applied to the investigation of UV absorption of benzene, furan, and 2-phenylfuran, and of fluorescence of 2-phenylfuran. 

Figure 23.2 The Visible Portion of the Hydrogen Atom Emission Spectrum (Simulated). Each wavelength represented produces an image of the slit of the spectrograph. If only discrete wavelengths are present, as in this case, the spectrum is called a line spectrum.

It is possible to model the vibronic bands in some detail. This has been done, for example, by Liu et al. (2004) forthe 6d-5f emission spectrum of Pa4+ in Cs2ZrCl6, which is analogous to the emission spectrum of Ce3+. However, most of the simulations discussed in this chapter approximate the vibronic band shape with Gaussian bands. The energy level calculations yield zero-phonon line positions, and Gaussian bands are superimposed on the zero-phonon fines in order to reproduce the observed spectra. Peaks of the Gaussian band are offset from the zero phonon fine by a constant. Peak offset and band widths, which are mostly host-dependent, may be determined from examination of the lowest 5d level of the Ce3+ spectrum, as they will not vary much for different ions in the same host. It is also common to make the standard... 

Fig. 15. Rotatory artifacts that simulate Cotton effects at an absorption band. The dependence of the rotatory artifact on absorbance of p-cresol solutions placed in series with the same poly-L-glutamic acid solution is shown. The concentration of p-cresol was adjusted to give the total absorbance of chromophore plus polypeptide background that appears with each curve. The rotator, poly-L-glutamic acid, was at concentration of 0.5% at pH 7.0 in a 10-cm cell. The rotations are those actually observed, a, in degrees. The rotatory dispersion at Am 2 coincides almost exactly with that for the polypeptide alone, so that it has been omitted from the figure. At Am 4, an interference filter, /, with maximum transmission between 280 and 285 m/i, was placed in the optical path. The absorption spectrum, in arbitrary units, is typical of p-cresol plus poly-L-glutamic acid background. The emission spectrum is represented in arbitrary units, uncorrected for detector response. (Urnes et al., 1961a.)...

We can employ the results of such simulations for both the Dirac and Schitidinger equations in order to calculate the HHG as well as the ATI spectra for the same laser parameters. This allows us to estimate the relativistic effects. An important observable is the multiharmonic emission spectrum S((o). It can be represented as the temporal Fourier transform of the expectation value of the Dirac (SchrOdinger) current density operator j(t) according to... 

In order to simulate the experimental emission spectrum (panel c) we have performed 3D wave-packet d3mamical calculations d20 Jacobi coordinates and the so-called DMBE potential energy surfaces of Varan-das et The result (for J = 0) is displayed in panel b and seen to... 

AS/NZ 4399 recommends that the polychromatic illumination should conform to the requirements of a solar simulator, i.e., in UV spectral distribution. However, as revealed by Fig. 14, this would only be relevant to quantifying the emission spectrum or whiteness of the sample. The source spectrum does not impose on the UV absorption measurement. 

Fig. 5 Simulated (TD-CAM-B3LYP/aug-cc-pVDZ) and experimental emission spectrum of 2-phenylfuran. Experimental data of Ref. [16] normalized by the maximum of the simulated data...

Figure 2. HF emission spectrum from the F + H CO reaction showing the match between the low resolution experimental spectrum from the monochromator and the computer-simulated spectrum, taken from ( 32)...

Either of the methods (ii) or (iii) discussed in section IV can be used to predict the vibrational structure. Both methods use classical trajectory input, both contain information about the spectroscopic initial state cj), and both make clear the role of nearly periodic classical trajectories as the main reason for a structured absorption or emission spectrum. Neither the wavepacket nor the moving phase space density computed with a swarm of trajectories will show intermediate-resolution structure in the time domain (and thus structure in the frequency domain) unless the trajectories make return visits at short or intermediate times. The spectrum obtained from method (ii) or (iii) simulates a true molecular absorption spectrum. 

Osmann et al. [33] investigated the Renner A X A" system of HO2, and used Eqs. (4—8) to represent their ab initio DMSs and TDMS (five surfaces) of this molecule computed with MRD-CI (Davidson-corrected) employing the cc-pVTZ basis sets both for oxygen and hydrogen atoms as well as the effective core potential (ECP) for oxygen. Emission spectrum at T =350 K was simulated, vibrational transition moments were eomputed and tabulated, see Fig. 4. 

Fig. 4 A simulation of the electric dipole emission spectrum of HO2 from 6915 to 7115cm by Osmann et al. [33] T = 350 K, W < 10 (rotational quantum number). Reprinted from Ref. [33], Copyright 1999, with permission from Elsevier.

It is obvious from these experiments that the absorption spectrum of the Martian red surface can be simulated reasonably well by a non-unique variety of Fe rich phases or their mixtures as can the weak magnetism, so that a positive identification will probably only be possible, following further in situ analyses and/or sample return and analysis in the lab.Two Mars Exploration Rovers (MERs) are due to arrive at Mars in 2004 and will attempt to analyze rocks and soils on the surface using several small spectrometers, including PanCAM (an extended visible region spectrometer), MiniTES (a thermal emission spectrometer), APXS (alpha proton X-ray spectrometer measuring the major elements), Mossbauer (run at current local temperature), as well as a 5-level magnet array similar to that on-board the Pathfinder Lander. 

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