Accurate comparison of Hel, NeI photoionization and He(23, 1 S), Ne(3s 3 P s,3 P 0) penning ionization of argon atoms and dimers

The Possible Role of Penning Ionization Processes in Planetary Atmospheres

“…It is well known that these observables depend on the strength, range, and anisotropy of the effective intermolecular interaction controlling the stereodynamics in the entrance Rg * -M (neutral) and the exit Rg-M + (ionic) channels of ionizing collisional events. In particular, when the position of the maximum of a certain peak in the PIES spectrum exhibits a sizeable negative shift, here referred to as εmax, with respect to the nominal energy, ε0 (defined as the difference between the excitation energy of the metastable He * or Ne * atoms and the ionization potential of the relevant molecular state), this is an indication that a phenomenological global attractive interaction drives the collision dynamics of the partners on a multidimensional potential energy surface, including entrance and exit channels [23,36]. These energy shifts are also determined by looking at the relative position of the corresponding peak maxima in the PES and PIES spectra.…”

“…This can be easily achieved because the microwave discharge produces not only metastable atoms but also many He(I) and Ne(I) photons, having an energy comparable to that of metastable atoms. To calibrate the electron transmission efficiency and the electron energy scale, some He * -H2O, H2S, NH3 PIES, and Ne(I)-H2O, H2S, NH3 PES spectra have been measured by exploiting the microwave discharge beam source: in the first case we use for the energy calibration the weak electron signal by He(I) photons of 21.22 eV, whereas in the latter case we record a PES spectrum, using the discharge source in pure neon producing a high intensity of Ne(Iα,β) photons [22,34], essentially of 16.84 and 16.66 eV, respectively, in a α:β ratio of about 5.3, checked by photoelectron spectrometric measurements of Kr atoms [35,36]. By comparison of our measurements with the expected spectrum as obtained from the He(I) radiation by Kimura et al [37], we calibrate the ionization energy scale.…”

“…By comparison of our measurements with the expected spectrum as obtained from the He(I) radiation by Kimura et al [37], we calibrate the ionization energy scale. The resolution of our electron spectrometer is ~45 meV at a transmission energy of 3 eV, as determined by measuring the photoelectron spectra of Ar, O2, and N2 by He(I) radiation with the procedure described in previous papers [18,36]. Spurious effects due to the geomagnetic field have been reduced to ≤20 mG by a μ-metal shielding.…”

A Theoretical and Computational Approach to a Semi-classical Model for Electron Spectroscopy Calculations in Collisional Autoionization Processes

“…In general, such a source was employed by using a ≈6 or ≈10 Torr inlet pressure of pure Helium or Neon, respectively. When we use such a device performing Penning ionization experiments with Ne * metastable atoms, we are producing both metastable atoms and a high intensity of Ne(I α,β ) photons, essentially of 73.6 and 74.4 nm wavelength respectively, in a α:β ratio of about 5.3, checked by photoelectron spectrometric measurements of Kr atoms [22,25]. The use of the microwave discharge beam source allows us also to calibrate the electron transmission efficiency and the electron energy scale in our PIES measurements by recording photoionization spectra for the investigated systems and comparing them with data reported in literature [42].…”

“…For example, ions formed by UV photo-ionization or by collision with excited species, are extremely important for the transmission of radio and satellite signals, and they govern the chemistry of planetary ionospheres [12,20,21]. In fact, since more than twenty years, our studies have shown that, when atoms and simple molecules (like for example H, O, rare gas atoms, and N 2 molecules) are subjected to electrical discharges, they can produce a large amount of species in highly excited electronic metastable states (see the following Table 1) [22][23][24][25][26]. Table 1.…”