APPLIED QUANTUM THEORY IN THE CLASSROOM: SPECTROSCOPIC STUDY OF GLOW DISCHARGES

Emission spectroscopy is a powerful tool to demonstrate how quantum theory can be applied with experimental data. Recent advances in low-cost array detector and inexpensive commercial systems combined with the availability of powerful computers and software packages have made feasible the introduction of these important topics into the undergraduate curriculum. In this paper, we demonstrate that it is possible the integration of classroom and laboratory when we applied the quantum theory. We present easy and inexpensive experiments, suitable to derive information on vibrational and rotational structures of electronic bands, intensity of these, as well as dissociation energy of different electronic states. Emission spectra of both positive column (PC) and negative glow (NG) regions of the dc glow discharge have been measured for different gases (CO2, N2 and O2). From the glow discharge emission spectra of CO2, we have identified O2, N2, CO species formed in excited electronic states. From the vibrational analysis of C3?u B3?g transition for N2, we have obtained the ?e”, ?exe”, ?e’, ?exe’ vibrational constants corresponding to electronic states involved in this band. We also determined D0 dissociation energy for C3?u y B3?g states of N2, using Birge-Sponer lineal extrapolation. We have also compared the experimental intensities of vibrational bands of several electronic systems of CO and N2 with the corresponding theoretical values. From spacing values for rotational lines of v’=0-v”=0, 1, 2, 3 and 4 bands of B1?+ A1? system of CO, we have obtained the Bv’=0 and Bv”=0 constants. Glow discharge temperatures were also estimated by spectroscopic methods.