Simulation of hyperfine-rotational spectrum of electromagnetic dipole transition rotation of BrF molecules br

The transition dipole of the hyperfine-rotation spectrum of J = 1 <- 0 within the vibronic ground (X1S, v =0) state of BrF molecule is derived, and thus, the transition selection rules are summarized as follows: DJ = +/- 1;DF1 = 0, +/- 1 and DF = 0, +/- 1, and those of DF1 = DF are intense while those of DF1 not equal DF are weak. Somespectral lines result from both the electric dipole transition and nuclear magnetic dipole transition due toperturbations, however, the magnetic dipole transition only contributes about one-billionth in the spectralintensity. The spectral linewidth is determined to be about 18 kHz by calculating the spectral transitionprobability. The obtained spectral linewidth and relative intensities are consistent with the experimental results.Additionally, the hyperfine-rotation spectral positions are determined by diagonalizing the Hamiltonian matrixin the basis of |JI1F1I2F, which is also in good agreement with the experiments within 10-8 (one-fiftieth of thespectral line width). Hence, the microwave hyperfine-rotation spectrum is simulated. In addition, we find thatthe nuclear spin-spin interaction not only slightly shifts the hyperfine-rotation spectral positions but alsochanges the sequence of the spectra. As to those unavailable constants of molecules, the fairly precise molecularconstants can be achieved by quantum chemical calculation, say, by employing MOLPRO program, and thenthe simulated spectra can guide the spectral assignment. Besides the guidance of spectral assignment, ourresults are also helpful for other relevant applications such as in absolute single quantum state preparation.

Automated summary

The transition dipole and selection rules of the hyperfine-rotation spectrum for J = 1 <- 0 in the BrF molecule's vibronic ground state are derived. The spectral lines are a result of both electric and nuclear magnetic dipole transitions, with the latter making a minimal contribution to the intensity. The spectral linewidth is determined to be approximately 18 kHz, and the positions of the spectral lines are accurately simulated through diagonalization of the Hamiltonian matrix. Additionally, the nuclear spin-spin interaction affects both the spectral positions and the sequence of the spectra. Quantum chemical calculations can provide precise molecular constants for spectral assignments.