The Electronic Spectrum of HF⁺

Abstract

The A2Σ+–X2Π emission spectrum of HF+, between 3580 and 4830 Å, has been photographed at high resolution and measurements on eight bands are reported. The analysis yields rotational and vibrational constants of the X state for ν = 0 to 2 and of the A state for ν = 0 to 3. A predissociation by rotation in the A2Σ+ state is observed and yields a dissociation energy of 3203 ± 50 cm−1 above the ν = 0, N = 0 level of this state. It is shown that this corresponds to a dissociation into H+(1S) + F(2P1/2). A detailed comparison with previous results obtained from photoelectron and photoionization experiments and from recent theoretical calculations is given.

Penning ionization and photoionization electron spectrometry of hydrogen fluoride

“…In this way we derived the adiabatic ionization potential value for the HF + (X2H3/2) state as 16.046 +0.001 eV [28]. Since the spectroscopic fine-structure splitting of 36.270 __+ 0.002 meV [26] and the theoretical fine-structure branching ratio of 1.195 [28] enter the calculated spectrum used in our fit procedure as fixed parameters, we can only state that they are compatible with our experimental data and, therefore, we do not assign error bars to them. These results are in excellent agreement with the best, so far available, PES data of Walker et al [42] who reported a value of the lowest ionization potential of HF of 16.044_+0.003 eV and a value of the spin-orbit coupling constant of 0.036_+0.001 eV.…”

“…Dissociative processes within H F + have also been studied by laserion beam photofragment spectroscopy [24] and H + translational energy spectroscopy [25]. The H F + (A 222 + -X 2 H i ) emission band system has been recorded at high resolution from which molecular constants were derived [26]; it was observed that there was an abrupt rotational break-off in the v' = 3 level at N' = 3, whereas Cosby et al [24] observed a termination at N ' = 4 in v' = 3 in their photofragment spectroscopic study of HF +. Another emission spectroscopic study yielded radiative lifetimes o f H F + (A 2X+, v' = 0-3) [27], although Werner et al [7] argued that the measured lifetimes are not pure radiative lifetimes but rather lifetimes shortened possibly by experimental space-charge effects.…”

Ab initio Cl calculation of the effects of Rydberg-valence mixing in the electronic spectrum of the HF molecule

“…In the simple model this energy difference should amount to approximately the 2//_ 227+ separation in HF +, i.e. more than 3eV (28)(29)(30). The configurations corresponding to the lowest such states of 1Z+ symmetry, for example, namely o-~no Table 9 (n>5) -or a~3s, 3p~r, 3da in the more conventional nomenclature -are all contained in the reference set (Table 6), but as expected they do not occur with sizeable coefficients in the expansion for the three lowest 1S + roots at the HF distances employed, For the 3S+ states more than three roots are calculated at a few small bond lengths and of the two additional roots the first, labelled 3X/~ a, does indeed correspond to configurations a~5a 1 and a~8a 1 with squared coefficients of 86~ and 5.5~o respectively at 1.5 bohr and 57~ and 12~o at 1.7 bohr; obviously mixing with other 3X+ states occurs for larger HF separations not investigated further.…”

Theoretical study of the He–HF+ complex. I. The two asymptotically degenerate ground state potential energy surfaces

“…The secondary minimum for linear He-FH (ϭ180°) is affected even less and in general for large angles the PES is very insensitive to r. ϭ91.5 cm Ϫ1 can be compared with 3090.5 and 89.0. 30 The minimum in the total 3D potential is at Rϭ2.231 Å and r ϭ1.0273 Å and the well depth of the intermolecular potential at this geometry is 1790.3 cm Ϫ1 ͑an increase of 159.0 cm Ϫ1 with respect to the value for rϭr e ). The intramolecular energy of HF ϩ is raised by 87.0 cm Ϫ1 with respect to its equilibrium value; the dissociation energy of the complex with respect to HF ϩ in its equilibrium geometry is 1703.6 cm Ϫ1 .…”