Un diagnostic pour enseigner les sciences à l'université

Dans cette étude, nous présentons un questionnaire diagnostic auquel ont participé 192 étudiants de première année universitaire, inscrits dans des filières scientifiques différentes : sciences physiques, sciences géographiques, sciences géologiques, sciences biologiques et médecine vétérinaire. Ce questionnaire, présenté aux étudiants en février 2021, est composé de quatre tests : le premier permet de mesurer le niveau d’abstraction des étudiants ; le second sonde la pensée formelle ; le troisième récolte des conceptions premières en sciences physiques et le quatrième s’intéresse à la psychologie cognitive. Les résultats sont analysés et présentés selon la filière, le genre et l’ancienneté académique (primo-arrivant ou redoublant) des étudiants. En s’appuyant sur les recherches menées par Piaget, une cartographie du niveau cognitif atteint par les étudiants est également établie. Nous constatons la récurrence de certaines difficultés

Study of acetylene diluted in xenon by diode-laser spectroscopy : I. Temperature dependence of the broadening coefficients

International audienceIn this paper, we present the Xe-broadening coefficients of 18 rovibrational lines in the band of (near 1330 cm−1) determined at five temperatures, ranging from 173.2 K to 298.2 K. The measurement of these coefficients was realized with a tunable diode-laser spectrometer. A low temperature cell was coupled with the spectrometer in order to determine their temperature dependence. The line parameters were obtained by fitting the experimental profiles by the Voigt lineshape and the Rautian and the Galatry models, which take into account the collisional narrowing. The results were compared with previous experimental data reporting for other vibrational bands and agree with them. This indicates that they are insensitive to vibrational excitation

Comparison of classical, semiclassical and quantum methods in hydrogen broadening of acetylene lines

International audienceQuantum close coupling (CC) calculations of H2-broadening coefficients of infrared and isotropic Raman lines of acetylene (C2H2) are performed for temperatures between 77 and 2000 K. They are used to test three more approximate methods, the quantum coupled states (CS) theory, the semiclassical Robert-Bonamy (RB) formalism and the full classical (FC) model of Gordon. In order to allow a clear and well founded comparison, all the dynamical calculations were performed employing the same ab initio potential energy surface free of any adjustable parameters. It is shown that below room temperature both the coupled states method and full classical method fail at reproducing the close coupling pressure broadening coefficients while above room temperature they are correct and predict comparable accurate values for temperatures greater than about 1000 K. The values provided by the RB method are clearly not satisfactory even at the highest temperature examined. However, the temperature dependence of the RB results follows the functional form used for interpolating and extrapolating CC, CS and FC pressure broadening coefficients