Spectra is a program for paramagnetic ions energy levels calculations. It allows to calculate electronic structure of all elements with unfilled f-shells, including lanthanides and actinides in crystalline hosts. It could be used in scientific research, educational institutions, industry (laser materials, chemical analysis etc).
User friendly Windows interface allows to customize the number of terms to be included in calculation (up to all terms in a given electronic configuration), obtain the values of reduced matrix elements for all d- and f-elements.
Crystal field parameters could either be adjusted to fit experimental levels or calculated using exchange charge model (not included in this version). Fully consistent J-J' mixing is included for crystal field of any symmetry. Optical and ESR spectra can be analyzed using unified approach with exact decomposition of wavefunctions for each specific energy level.
Free-ion Hamiltonian for f-electrons includes Coulomb interaction; configurational interaction; spin-orbit coupling; spin-spin and spin-other-orbit interaction, correction to spin-orbit coupling due to configuration interaction. Total number of free-ion parameters is 19: F2, F4, F6 for Coulomb interaction; dzeta for spin-orbit coupling; alpha, beta and gamma for two-body integrals in configuration interaction; T2, T3, T4, T6, T7, T8 for three-body configuration interaction; M0, M2, M4 for Marvin integrals of magnetic interactions; P2, P4, P6 for spin-orbit corrections due to configuration interaction.
For the fitting of experimental levels the user should create an ASCII file with .exp extension in c:\spectra\exp folder, containing in increasing order the values for experimental energy levels. If some of the levels are not available, a value of 1 should be put instead. These levels will not be fitted. The minimum number of different experimental levels is n, where n is the number of fitting parameters. The fitting algorithm is a variation of differential evolution method. It conducts a global search in parameters space. Hence, results of fitting are not critically dependent on initial values for parameters. The trade-off is slower performance - each fitting would require typically several hundreds of matrix diagonalization. In the next version the option for fast fitting based on Levenberg-Marquardt algorithm will be included.
This software is in a testing stage and it is not optimized neither for speed nor for memory usage. It was tested on Pentium-150 MMX with 32 MB RAM under Windows NT/Windows 95. However, some of the features will work on low end computers as well.
File db.zip should be unzipped to the root C:\ folder. After installation the folder with name "Spectra" should appear together with three subfolders: C:\Spectra\Lev; C:\Spectra\Des; C:\Spectra\Exp.
File spectra.zip contains the last current version of SPECTRA executable file. To upgrade to the latest version only old spectra.exe file needs to be replaced in C:\spectra directory. However, latest db.zip file can contain extra records for recently studied hosts doped with f-ions.
You can download latest spectra.hlp file and put it into C:\Spectra folder for access from SPECTRA program. Manual in PDF format for printing a hard copy is also available.