1,720,976 research outputs found
Basic molecular processes for hydrocarbon spectroscopy in fusion edge plasmas: vibrationally state-selective excitation of A (2)Delta, B (2)Sigma(-) and C (2)Sigma(+) states of CH by electron impact
No full textQuantification of chemical erosion in fusion edge plasmas is often based upon CH (Gero-band) spectroscopy. Systematic, vibrationally resolved rate coefficients for the electron impact excitation of A (2)Delta, B (2)Sigma(-) and C (2)Sigma(+) electronic states of the CH molecule are presented in the temperature range 0.2-1500 eV. The rate coefficients for 0-0 vibrational transitions are based on the R-matrix cross sections for energies below 10 eV, Born-Bethe cross sections for energies above similar to 25-30 eV and a smooth interpolation in the 10-20 eV energy range. The rate coefficients for the v-v' transitions are determined by using a scaling relationship. The implications of these results for the fusion edge/divertor plasma diagnostics, based on the A(v') -> X(v) transitions, are discussed. The rate coefficients for the 0-0 transitions are presented by convenient analytic fit expressions
Electron-impact-induced allowed transitions between triplet states of H2
No full textElectron-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
Total and dissociative electron-impact cross sections for X-1 Sigma(+)(g) -> B-1 Sigma(+)(u) and X-1 Sigma(+)(g) -> C-1 Pi(u) transitions of vibrationally excited tritium and deuterium-tritium molecules
No full textElectron-impact fetal and dissociative cross sections, calculated by using the impact-parameter method, for the X(1)Sigma (+)(g) --> B(1)Sigma (+)(u) and X(1)Sigma (+)(g) --> C(1)Pi (u) transitions of vibrationally excited T-2 and DT molecules, are presented. The mass and vibrational energy scalings of these cross sections are discussed
Scaling of electron-impact dissociative ionization cross sections of vibrationally excited H2 and D2 molecules
No full textA scaling law for electron-molecule collision cross sections for dissociative ionization of vibrationally excited H-2 and D-2 molecules is given as function of the collision energy and the vibrational quantum number
State-to-state electron impact cross sections for BeH+ molecular ions in ITER-like fusion edge plasmas with Be walls
No full textBeH+ molecules will be an important intermediary species present in fusion plasmas with Be walls (e.g. JET, ITER), both for impurity transport and spectroscopic studies. To enable such analyses the electron-impact-induced excitations X (1)Sigma(+)(v(i)) -> A (1)Sigma(+)(v(f)) and X (1)Sigma(+)(v(i)) -> B (1)Pi (v(f)) in BeH+(v(i)) molecular ion, occurring between the v(i) and v(f) vibrational levels of different electronic states (vibro-electronic transitions), have been studied using the Coulomb-Born approximation. The cross sections and rate coefficients for these transitions have been calculated in a broad energy and temperature range, respectively. Accurate analytic fit expressions have been derived for the cross sections and rate coefficients for the v(i) = v(f) = 0 case of considered electronic transitions that have correct asymptotic limits. It has been demonstrated that the cross sections and rate coefficients for v(i), v(f) > 0 transitions satisfy approximate (to within 10%) scaling relationships that involve the transition energies and matrix elements of dipole transition moments only
Electron-impact excitation cross sections of vibrationally excited X (1)Sigma(+)(g) H-2 and D-2 molecules to Rydberg states
No full textA complete set of total and dissociative electron-impact cross sections of vibrationally excited H-2 and D-2 molecules has been calculated by using the impact-parameter method. Transitions to low-lying Rydberg states (X-->B' ,X-->B ", X-->D, X-->D') are considered. Finally, vibrational and mass scaling relations, able to reproduce the calculated cross sections, are presented. [S1050-2947(99)00609-5]
Cross sections for 14-eV e-H(2) resonant collisions: Isotope effect in dissociative electron attachment
No full textThe process of dissociative attachment of electrons to molecular hydrogen and its isotopes in the energy range at approximately 14 eV is investigated. The dissociative electron attachment cross sections for all six hydrogen isotopes are calculated over an extended range of electron energies using the local complex potential model with the excited Rydberg (2)Sigma(+)(g) electronic state of H(2)(-) acting as the intermediate resonant state. A significant isotope effect in theoretical electron attachment cross sections is observed, in agreement with previous predictions and experimental observations. A two-parameter analytic expression for the cross section is derived from the theory that fits accurately the numerically calculated cross sections for all isotopes. Similarly, an analytic mass-scaling relation is derived from the theory that accurately reproduces the numerically calculated rate coefficients for all isotopes in the 0.1-1000 eV temperature range by using the rate coefficient for the H(2) isotope only. The latter is represented by an analytic fit expression with two parameters only
Cross sections for 11-14-eV e-H2 resonant collisions: Vibrational excitation
No full textResonant vibrational excitation (RVE) cross sections have been calculated for the electron-H(2) molecule collisions in the energy range 11-14 eV involving the (2)Sigma(+)(g) excited electronic state of the molecular hydrogen ion H(2)(-). 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 (2)Sigma(+)(g) resonant state. The cross sections for all nu(i)=0 ->nu(f)=1-14 RVE transitions have been calculated. A satisfactory agreement of calculated cross sections with the available experimental data is obtained
Electron molecule cross sections relevant to negative ion sources and divertor plasmas.
No full textElectron‐molecule cross sections for electronic transitions in H2 and D2 molecules vibrationally excited are presented, and a scaling law for the vibrational cross sections is discussed for the X1∑+g→B1∑+u electronic transition
Cross sections for 14-eV e-H2 resonant collisions: Dissociative electron attachment
No full textThe dissociative electron attachment (DEA) process in electron-H(2) molecule collisions, involving the (2)Sigma(+)(g) excited electronic Rydberg state of molecular hydrogen ion H(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
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