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Magnetic rotation study of the A3[pi]1u-X1[epsilon]g+ system of 79Br2 Boone, Christopher D.


The A³ Π ₁[sub u]-X¹Σ⁺[ sub g] system of ⁷⁹Br₂ has been studied using magnetic rotation spectroscopy. A new procedure has been introduced to simplify the calculation of magnetic rotation spectra. The A state was investigated over a range of vibrations 13 < v < 37, which extended to within 2 Cm⁻¹ of the dissociation limit for the A state. A global analysis was performed on the A state, making use of near-dissociation expansions. From the global analysis, the following parameters were obtained: D (dissociation energy, relative to v = 0, J = 0 in the ground state) = 15,894.619 ± 0.007 cm⁻¹, v[sub D] (effective vibration at dissociation) = 41.544 ± 0.013 and C₅ (a parameter describing the long-range form of the potential) = 61,700 ± 900 cm⁻¹ A⁵. From the potential curve generated in the global analysis, the following spectroscopic parameters were determined for the A state: r[sub e] (equilibrium distance) = 2.7026 Å, Be (equilibrium rotational constant) = 0.05849 cm⁻¹, D[sub e] (binding energy) = 2147.82 cm⁻¹, and T[sub e] (energy relative to the minimum of the X state potential) = 13,909.14 cm⁻¹. From an analysis of the long-range potential of the A state, it was determined that the dissociation energy relative to v = 0, J = 0 in the ground state was 15,894.58 ± 0.01 cm⁻¹; this differed significantly from the value obtained in the global analysis, a consequence of the fact that the global analysis gave effective values for the parameters determined. The Ω-type doubling constant in the A state was observed to level off as a function of v above v = 19. Structure in low-J lines was attributed to hyperfine structure in the A state. Extra lines were observed in the spectrum, including an entire series of extra lines associated with v = 27 in the A state that extended over a range of J from 2 to 32. Many of these extra lines, including the extra series, arise from perturbation-allowed transitions to levels in the A’³Π₂[sub u] electronic state. Using the extra lines, an estimate was made for the energy of the A' state (relative to the bottom of the potential in the ground state): 13,187 ± 20 cm⁻¹.

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