Collective phenomena in pp and ep scattering

Bjorken scaling violation in deep inelastic electron-proton scattering (DIS) is related to the rise of hadronic cross sections by using the additive quark model. Of special interest is the connection between saturation in the low-x behavior of the DIS structure functions (SF) and possible slow-down of the pp cross section rise due to saturation effects. We also identify saturation effects in the DIS SF with phase transition that can be described by the Van der Waals equation of state

Cross sections for 11–14-eV e-H2 resonant collisions: Vibrational excitation

Resonant vibrational excitation (RVE) cross sections have been calculated for the electron-H2 molecule collisions in the energy range 11–14 eV involving the 2Σ+g excited electronic state of the molecular hydrogen ion H2−. This state, whose threshold is located around 14 eV, gives rise to the so-called series a of the observed peaks in electron-impact differential cross-section measurements. The calculations have been performed within the local complex potential approximation by using the available theoretical potential energy and width for the 2Σ+g resonant state. The cross sections for all vi=0→vf=1–14 RVE transitions have been calculated. A satisfactory agreement of calculated cross sections with the available experimental data is obtained

Cross sections for 14-eV e-H2 resonant collisions: Dissociative electron attachment

The dissociative electron attachment (DEA) process in electron-H[sub]2 molecule collisions, involving the ^2Σ^+[sub]g excited electronic Rydberg state of molecular hydrogen ion H[sub]2^−, is investigated theoretically. The DEA cross section has been calculated within the local complex potential approximation. The convoluted cross section, which presents a peak located at the incident energy of about 14 eV, compares favorably with available experimental data

Electron-impact vibrational excitation of vibrationally excited H2 molecules involving the resonant 2(Sigma)g+ Rydberg-excited electronic state

Electron-impact theoretical cross sections and rate coefficients for vibrational excitation of vibrationally excited H2 molecules, occurring through the H−2 resonant species in the 2Σ+g Rydberg-excited electronic state, are presented. The cross sections are calculated as functions of the incident electron energy by adopting the local-complex-potential model for resonant collisions and by using ab initio calculated molecular potentials and resonance widths. The calculations have been extended to all possible vibrational transitions linking all 15 vibrational levels of the electronic ground state of the H2 molecule. The corresponding rate coefficients are also obtained as a function of the electron temperature by assuming a Maxwellian electron energy distribution function, and a simple analytical expression is derived. Finally, the present rate coefficients for the transitions starting from the lowest vibrational level of the H2 molecule are compared with those for the process involving the X2Σ+u resonant state of the H−2 molecular ion

Molecular physics of elementary processes relevant to hypersonics: Electron-molecule collisions

Non-resonant, electron-impact, vibro-electronic excitation cross sections, involving vibrationally excited N2 molecules, to the mixed valence-Rydberg b,c,o 1Πu and b′,c′,e′ 1åu+ singlet states are presented. These cross sections are calculated using the so-called similarity approach, accounting for the vibronic coupling among excited states, and compared with the experiments and different theoretical calculations. New cross sections for the electron-impact resonant vibrational excitation of CO2 molecule are calculated, for the symmetric stretching mode, as a function of the incident electron energy and for the transitions (υ i , 0,0)→(νf , 0,0) with νi = 0,1,2 and for some selected value of νf in the interval νi ≤νf ≤10. A resonance potential curve and associated widths are calculated using the R-matrix method. Rate coefficients, calculated by assuming a Maxwellian electron energy distribution function, are also presented for the same (νi , 0,0)→(νf , 0,0) transitions. Electron-impact cross sections and rate coefficients for resonant vibrational excitations involving the diatomic species N2, NO, CO, O2 and H2, for multi-quantic and mono-quantic transitions, are reviewed along with the cross sections and rates for the process of the dissociative electron attachment to H2 molecule, involving a Rydberg excited resonant state of the H2- ion

Electron impact induced allowed transitions between triplet states of H2

Electron-impact-induced excitation and dissociation processes between the excited triplet states a (3)Sigma(g)(+)-->d (3)Pi(u), c (3)Pi(u)-->h (3)Sigma(g)(+), and c (3)Pi(u)-->g (3)Sigma(g)(+) of molecular hydrogen are studied by using the impact-parameter method. The cross sections for nu(i)-nu(f) resolved vibronic transitions between states have been calculated in the energy range from threshold to 100 eV; their maxima being located in the region of 5-10 eV. A special treatment was required for the transition to the h (3)Sigma(g)(+) state, whose adiabatic potential-energy curve possesses a barrier at the internuclear distance of about 5a(0), sustaining three quasi-bound vibrational states with widths of 5.3x10(-12), 1.5x10(-3), and 42.0 cm(-1), respectively. The quasistationary character of these vibrational states is taken into account when calculating the c (3)Pi(u)-->h (3)Sigma(g)(+) excitation and dissociation cross sections