Synopsis In this work we report calculations of potential energy curves in the 1.2a.u. ≤ R ≤ 100a.u. range at the Multireference Configuration Interaction (MRCI) level for doubly excited states of ...the H2 molecule. The molecular state which dissociates into two H(2s) atoms is clearly identified. The Generalized Oscillator Strength as a function of transferred momentum for three doubly excited states is also presented.
In this work we present our results for calculations of doubly excited states of potential curves of H2 and the corresponding double excitation cross sections by electron impact using the First Born ...Approximation. The wave functions and potential energy curves were calculated using the Configuration Interaction method.
A method for the determination of ethambutol (EMB), a first-line drug against tuberculosis, based on CE with capacitively coupled contactless conductivity detection is proposed. The separation of EMB ...and its main product of degradation were achieved in less than 3 min with a resolution of 2.0 using a BGE composed of 50 mmol/L histidine and 30 mmol/L MES, pH 6.30. By raising the pH to 8.03, the analysis time was reduced to 1.0 min, but with a significant loss of resolution (0.7). Using the best separation conditions, linearity of 0.9976 (R², five data points), sensitivity of 1.26x10⁻⁴ V min μmol⁻¹ L, and LOD and quantification of 23.5 and 78.3 μmol/L, respectively, were obtained. Recoveries at four levels of concentration ranged from 95 to 102% and the concentration range studied ranged from 100 to 500 μmol/L. The results obtained for the determination of EMB in pharmaceutical formulations were compared with those obtained by using CE with photometric detection.
In order to simulate the effects of energetic charged particles present in the solar wind colliding with the cometary gaseous formic acid molecule (HCOOH), laboratory experiments have been performed. ...The absolute ionization and dissociation cross-sections for this molecule interacting with solar wind particles were measured employing fast electrons in the energy range of 0.5 to 2 keV and energetic protons with energies varying from 0.128 to 2 MeV. Despite the fact that both projectiles lead to a very similar fragmentation pattern, differences in the relative intensities of the fragments were observed. Formic acid survives about four to five times more to the proton beam than to the energetic electron collision. The minimum momentum transfer in the electron impact case was estimated to be 3-38 per cent larger than the minimum momentum transfer observed with the equivelocity protons. The ultraviolet (UV) photodissociation rates and half-lives for HCOOH are roughly closer to the values obtained with energetic electrons. It is consequently important to take electron impact data into account when developing chemical models to simulate the interplanetary conditions.
We have investigated the production of metastable H(22S) coming from the dissociation of cold H2 molecules by electron impact. Two detectors have analysed the neutral fragments as a function of their ...time-of-flight through localized quenching of H(22S) in H(22P) and Lyman-a detection.
We have produced slow metastable H(2
2
S
1/2
) coming from the dissociation of cold H
2
induced by electron collisions. The experiment consisted of a supersonic jet of H
2
crossing electrons produced ...by a high intensity pulsed electron gun. The neutral fragments were detected through electric field induced Lyman-
α
radiation and their velocities were measured by time-of-flight (TOF) technique. The main characteristics of our experiment are the low molecular temperature, the long flight path and the small well defined collision and electric field regions. They give rise to precise velocity measurements and, consequently, to good spectra resolution. We have performed a careful analysis of the electron-molecule collision kinematical effects in order to identify which vibrational levels can be involved in the transition. Our results also explain the origin of the TOF peak widths. Relative probabilities to produce these levels have been deduced.
In this work we present a new experimental apparatus being set up in Rio de Janeiro to study coincidence detection of pairs of excited hydrogen atoms coming from the dissociation of a single H2 ...molecule by detecting emitted Lyman-alpha radiation.
PDF
