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Over 90 years ago, Alexander Graham Bell described qualitatively the results of a series of experiments which have gone virtually unnoticed by succeeding generations of molecular spectroscopists

Spectroscopic analysis of optical emission during rf plasma etching of semiconductor materials has been used to gain a better understanding of the plasma chemistry involved in these systems. The emission was studied principally in CF4-O2 gas mixtures, but other gases were observed as well. It is known that the addition of a relatively small percentage of O2 to CF4 yields a much faster etching rate for silicon and silicon nitride. With the addition of 02 to CF4 discharges we have studied emission from atomic O and molecular CO with a large increase in the emission of atomic F. When the plasma is actively etching silicon or silicon nitride, the emission intensities of both F and O atoms are significantly lower. The etching process can be monitored by observing the intensities of these lines. Analysis of the emission features has also been used to determine abnormal conditions which can adversely affect the etching process.

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The Franck–Condon factors for the Ã←X̃ transition in NH3 have been calculated and compared with the observed relative intensities of electron impact spectra. Calculations were made in which the symmetric bending mode was fitted as an anharmonic oscillator. In addition, the Franck–Condon factors were calculated for the case in which all vibrations were approximated as harmonic. The former calculations best fit the observed intensity distribution. The Ã←X̃ transition consists of overlapping bands in which the symmetric stretching and bending vibrations of the à state are excited. The symmetric stretching frequency of the ã state is estimated to be 2900 ± 50 cm−1.