Boltzmann Equilibrium Spectrum Program (BESP)

Selected diatomic molecular spectra are computed by use of so-called line strength files. For isolated molecular transitions, the Franck-Condon factors are found by numerically solving the radial Schrödinger equation, and the Hönl-London factors are obtained by numerical diagonalization of the rotational and fine-structure Hamiltonian. For the computation of a diatomic spectrum, typically the temperature and spectral resolution is specified, and in turn, non-linear fitting routines may be used to infer the spectroscopic temperature.

Of interest are diatomic molecules such as AlO, C₂, CH, CN, CrF, N₂⁺ 1stNeg, N₂ 1stPos, N₂ 2ndPos, NH, NO, OH. Accurate line-strength files are in use for spectroscopic analysis with BESP. The BESP is used, for example, in the analysis of laser-induced optical breakdown and laser-induced fluorescence. Selected synthetic spectra are given below.

High Resolution N2 2-nd positive Spectrum

High Temperature C2 Swan System Spectrum

High Temperature OH Spectrum

BESP has been written to be compatible with standard Operating Systems such as Linux or Microsoft. A detailed set of C2 Swan spectra is illustrated below, for temperatures between 2000 [K] and 7000 [K] with spectral resolutions between 2 [1/cm] and 8 [1/cm]. OH spectra are shown for temperatures between 1000 [K] and 7000 [K] with spectral resolutions between 2 [1/cm] and 64 [1/cm].

C2 Swan Δv = +1,0,-1 progression spectra between 450 [nm] and 570 [nm]

C2 Swan Δv = +1 sequence spectra between 450 [nm] and 475 [nm]

C2 Swan Δv = 0 sequence spectra between 475 [nm] and 520 [nm]

C2 Swan Δv = -1 sequence spectra between 520 [nm] and 570 [nm]

OH Δv = 0 sequence spectra between 305 [nm] and 322 [nm]

CN violet Δv = 0 sequence spectra between 375 [nm] and 390 [nm]