Computer-assisted analysis of singlet-triplet rotational spectra: application to case (A), case (B) and case (AB) coupling cases in polyatomic molecules Original Research Article

A non-graphical, character-based computer program for the least-squares analysis of the high-resolution rotational spectra of singlet-triplet transitions in orthorhombic molecules has been developed under the ANSI C programming language. The program is applicable to molecules which show either Hundʹs case (A) or case (B) or case (AB) type splittings. Up to 22 rotational, spin, centrifugal distortion and spin-centrifugal distortion constants may be varied. Only constants of the excited state may be fitted. The program has been tested under the HP-UX and DOS/Windows environments. J-values up to 255 can be accommodated in the UNIX version of the program while the DOS/Windows version is limited to J = 50. A compiled and linked executable file is available for the DOS/Windows version for those without access to a C compiler. A limited band contour capability is provided through the production of an ASCII file of frequency versus intensity for the calculated spectrum.