Theoretical calculations have been carried out on the X 2A 1, 1 2B2(3p), 2 2A1(3p), and 3 2A1(4s) electronic states of FH2. Equilibrium geometries and rotational constants as well as the first few vibrational levels of the excited states have been calculated, in order to obtain theoretical information on the 2 2A1(3p)→1 2B2(3p) and the 3 2A1(4s)→1 2B2(3p) transitions in FH2, which might be relevant to the observed spectra at about 7500 and 8000 Å. The results show that the equilibrium geometry of the first excited state of FH2, 1 2B2(3p), is quite different from those of the other excited states. The estimated transition energies (△E0) in FH2 are 1.68 and 1.97 eV for the transitions 2 2A 1(3p)→1 2B2(3p) and 3 2A 1(4s)→1 2B2(3p), respectively, while in FD2 the corresponding quantities are 1.65 and 1.95 eV, respectively. A search for a minimum on the ground state surface of FH2, which has been carried out near two saddle point geometries, has not found one. Thus the present calculations do not find a metastable ground state species.

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Journal The Journal of Chemical Physics
Petsalakis, I.D., Theodorakopoulos, G., Wright, J.S, & Hamilton, I.P. (1988). Theoretical investigation involving electronic and vibrational calculations of the 2 2A1(3p)→1 2B2(3p) and the 3 2A1(4s)→1 2B2(3p) transitions in FH2 and FD2. The Journal of Chemical Physics, 89(11), 6841–6849.