Synthetic spectra

Spectroscopic Probes of Cavitation Conditions. Determination of the temperatures reached ia a cavitating bubble has remained a difficult experimental problem. As a spectroscopic probe of the cavitation event, MBSL provides a solution. High resolution MBSL spectra from sUicone oU under Ar have been reported and analy2ed (7). The observed emission comes from excited state has been modeled with synthetic spectra as a... 

Fig. 14.3 (a) SBSL spectra containing Ar emission lines from 85% H2S04 and the best fit synthetic spectra at 15,000 K. (b) SBSL spectra and the low pressure spectra from a Hg(Ar) calibration lamp [11] (reprinted with permission from Annual Reviews)... 

Astronomical Observatory, were used to carry out the calculations of theoretical equivalent widths of lines, synthetic spectra and a set of plane parallel, line-blanketed, flux constant LTE model atmospheres. The effective temperatures of the stars were determined from photometry, the infrared flux method and corrected, if needed, in order to achieve the LTE excitation balance in the iron abundance results. The gravities were found by forcing Fe I and Fe II to yield the same iron abundances. The microturbulent velocities were determined by forcing Fe I line abundances to be independent of the equivalent width. For more details on the method of analysis and atomic data see Tautvaisiene et al. (2001). 

The observations were performed at ESO using the 1.52m telescope and FEROS. The obtained spectra have high nominal resolving power (R 48000), and S/N 500 at maximum and a coverage from 4000 A to 9200 A. Many spectra were acquired for all sample stars. The atmospheric parameters (Teff, log g, [Fe/H] and microturbulence velocities) have been obtained through an iterative and totally self-consistent procedure from Fe lines of the observed spectrum. The initial values of Teg were obtained from a (B-V) vs Teg calibration and log were determined from Hipparcos parallaxes and evolutionary tracks. The [O/Fe] abundances were derived by fitting synthetic spectra to the observed one. 

We have first explored the Li line region (670.7nm) for faint stars (bottom of the RGB, the RGB Bump area and the HB, see Fig.l). Data reduction has been done with the GIRAFFE DRS on 123 spectra (signal to noise ratio around 70). The log g have been estimated with a fit of the mean RGB and HB sequences of 47 TUC to a theoretical isochrone (Bertelli et al. 1994), and Teff have been estimated from the (V-I) color-temperature relations (Houdashelt et al., 2000). With [Fe/H]= - 0.65 for 47 TUC, synthetic spectra have been computed from MARCS models (log g= 3.0 TejJ= 4800 K to 5100 K). Li abundances (A Li>0 dex, Li dots in Fig.l) have been derived for 41 stars (with uncertainties of about 0.2dex). 

Fig. 1. CMD of our faint stars sample and selected (observed and synthetic) spectra.

Starburst 99 (Leitherer et al. 1999, 2001) gives synthetic spectra for actively star-forming galaxies assuming a selection of different ages, metallicities and initial mass functions. 

Fig. 12.3. Synthetic spectra for a region with constant star-formation rate for the ages indicated, assuming a Salpeter IMF cut-off at 75 MQ. After White (1989), based on computations by Gustavo Bruzual. With kind permission from Kluwer Academic Publishers. Courtesy Stephane Chariot.

Fig. 12.10. Comparison of the observed spectrum of the gravitationally lensed LBG MS 1512-cB58 (bold), with a redshift of 2.7, with synthetic spectra calculated with Starburst 99 together with the theoretical spectral library WM-basic for various metallicities (faint). The left panels show the region of the A. 1425 complex (a blend of Si, C and Fe photospheric lines), while the right panels show photospheric features of Fe hi between 1900 and 2000 A. After Rix etal. (2004).

The obtained "fit point" parameters are now used for the calculation of "final models 1, and the resulting synthetic spectra are compared with the observation as a final check. We restrict the representation (Fig. 1) to the model C, since the corresponding profile fits for the other two mass-loss rates would appear very similar. 

The first spectra which were synthesized using the R matrix approach were, not surprisingly, vuv spectra, and synthetic spectra of Mg, Ca, Sr, and Ba have all been calculated.22-25 In Fig. 19.2 we show the Ba vuv spectrum. While the region above the Ba+ 6p1/2 limit is understandable, the region below the limit exhibits... 

Spectroscopic Probes of Cavitation Conditions. Determination of the temperatures reached in a cavitating bubble has remained a difficult experimental problem. As a spectroscopic probe of the cavitation event, MBSL provides a solution. High resolution MBSL spectra from silicone oil under Ar have been reported and analyzed (7). The observed emission comes from excited state C2 and has been modeled with synthetic spectra as a function of rotational and vibrational temperatures, as shown in Figure 7. From comparison of synthetic to observed spectra, the effective cavitation temperature is 5050 =L 150 K. The excellence of the match between the observed MBSL and the synthetic spectra provides definitive proof that the sonoluminescence event is a thermal, chemiluminescence process. The agreement between this spectroscopic determination of the cavitation temperature and that made by comparative rate thermometry of sonochemical reactions is surprisingly dose (6). 

Figure 14 Frequency shifts of the composite symmetric CH2 stretching band in actual and synthetic spectra of 0.3 M DTAB/DDAB mixtures (T = 25°C). The squares are the data points from actual spectra, while the line is from synthetic spectra.

Figure 16 Comparison of real and synthetic spectra of 0.3 M DDAB/DTAB mixtures in the fingerprint region illustrating the band splitting in real spectra is not accounted for by spectral overlap (T = 25°C).

The band positions of the headgroup modes for the synthetic spectra in Figure 7 are the same as observed for the 0.40 M CgAO solution (Figure 5) ... 

Figure 7. Synthetic spectra of micellar solutions (0.40 M) of CgAO at Z equal 0,0.5,1.0.

Within the last 25 years of X-ray spectroscopy on fusion devices, the theory of He-like ions has been developed to an impressive precision. The spectra can be modeled with deviations not more than 10% on all lines. For the modeling, only parameters with physical meaning and no additional approximation factors are required. Even the small effects due to recombination of H-like atoms, which contribute only a few percent to the line intensity, can be used to explain consistently the recombination processes and hence the charge state distribution in a hot plasma. The measurements on fusion devices such as tokamaks or stellarators allow the comparison to the standard diagnostics for the same parameters. As these diagnostics are based on different physical processes, they provide sensitive tests for the atomic physics used for the synthetic spectra. They also allow distinguishing between different theoretical approaches to predict the spectra of other elements within the iso-electronic series. The modeling of the X-ray spectra of astronomical objects or solar flares, which are now frequently explored by X-ray satellite missions, is now more reliable. In these experiments, the statistical quality of the spectra is limited due to the finite observation time or the lifetime of... 

The calculations I ve presented here support the idea that SO2 self-shielding is at least in part responsible for the S-MIF observed in Archean rocks. Because of the approximations made in the SO2 isotopologue synthetic spectra, it caimot be claimed that SO2 photolysis is the only source of MIF. Experimental data needed to improve the isotopologue spectra include measurements of vibronic band shifts for all four sulfur isotopologues and for the and isotopo-... 

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