Search results for "computational spectroscopy"
showing 6 items of 6 documents
The partition sum of methane at high temperature
2008
11 pages, 4 Tables, 3 Figures Computer code on line at http://icb.u-bourgogne.fr/JSP/TIPS.jsp; International audience; The total internal partition function of methane is revisited to provide reliable values at high temperature. A multi-resolution approach is used to perform a direct summation over all the rovibrational energy levels up to the dissociation limit. A computer code is executable on line at the URL : http://icb.u-bourgogne.fr/JSP/TIPS.jsp to allow the calculation of the partition sum of methane at temperatures up to 3000 K. It also provides detailed information on the density of states in the relevant spectral ranges. The recommended values include uncertainty estimates. It is …
Extension of the MIRS computer package for the modeling of molecular spectra : from effective to full ab initio ro-vibrational hamiltonians in irredu…
2012
The MIRS software for the modeling of ro-vibrational spectra of polyatomic molecules was considerably extended and improved. The original version (Nikitin, et al. JQSRT, 2003, pp. 239--249) was especially designed for separate or simultaneous treatments of complex band systems of polyatomic molecules. It was set up in the frame of effective polyad models by using algorithms based on advanced group theory algebra to take full account of symmetry properties. It has been successfully used for predictions and data fitting (positions and intensities) of numerous spectra of symmetric and spherical top molecules within the vibration extrapolation scheme. The new version offers more advanced possib…
Multi-resolution error analysis of predicted absorption coefficients. Method and computer implementation. Application to the IR spectrum of methane a…
2009
A general method for the estimation of the confidence interval of molecular absorption coefficients is presented. It combines statistical numerical experiments with analytical calculations. The method uses line parameter predictions (position and intensity) with known estimated uncertainties. The propagation of errors from line parameters to absorption coefficients or cross-sections are analyzed in detail as a function of the resolution. This work is especially intended to provide expert information for applications requiring theoretical predictions for which the present state of the art of line by line high-resolution modeling is not accurate enough to meet the experimental precision. As a…
The STDS Dijon system : Present status and prospects.
2009
The Dijon spectroscopy group has developed powerful techniques based on group theory and tensorial formalism in order to analyze and simulate absorption and Raman spectra of molecules with various symmetries. Software packages and databases implementing these tools have been created [1]. Compared to the widely used spectroscopic databases (HITRAN, GEISA), these packages, with their XTDS common interface [2], are primarily devoted to the calculation of line parameters and spectra from a database of model parameters. Future developments include improved fitting algorithms, inclusion of C3v symmetric tops, rovibronic couplings, uncertainty estimates. Moreover, calculated line lists will be acc…
Multi-Resolution error analysis of predicted absorption coefficients. Method and computer implementation. Application to the infrared spectrum of met…
2009
A general method for the estimation of the confidence interval of molecular absorption coefficients is presented. It combines statistical numerical experiments with analytical calculations. The method uses line parameter predictions (position and intensity) with known estimated uncertainties. The propagation of errors from line parameters to absorption coefficients or cross-sections are analyzed in detail as a function of the resolution. This work is especially intended to provide expert information for applications requiring theoretical predictions for which the present state of the art of line by line high-resolution modeling is not accurate enough to meet the experimental precision. As a…
Pyrene, a Test Case for Deep-Ultraviolet Molecular Photophysics
2019
We determined the complete relaxation dynamics of pyrene in ethanol from the second bright state, employing experimental and theoretical broadband heterodyne detected transient grating and two-dimensional photon echo (2DPE) spectroscopy, using pulses with duration of 6 fs and covering a spectral range spanning from 250 to 300 nm. Multiple lifetimes are assigned to conical intersections through a cascade of electronic states, eventually leading to a rapid population of the lowest long-living excited state and subsequent slow vibrational cooling. The lineshapes in the 2DPE spectra indicate that the efficiency of the population transfer depends on the kinetic energy deposited into modes requir…