AN ELECTRONIC EMISSION SPECTRUM OF DIACETYLENE: A STUDY OF SCHULER'S ``T'' SPECTRUM UNDER HIGH RESOLUTION
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Date
1955
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Ohio State University
Abstract
Sch\""{u}ler has constructed a glow discharge tube in which can be studied the effect of introducing varying proportions of organic vapours on the spectrum of the positive column maintained by a ``carrier” of, for example, $helium.^{1}$ He describes a whole series of new emission spectra thus obtained from a number of organic $compounds,^{2}$ including one in the visible region which was common to many of them, and which he labelled ``T”. The latter which appeared most strongly, and to the exclusion of all others, on using $diacetylene^{3}$ he attributed to diacetylene itself.\\ His experiments have been repeated and the ``T” spectrum photographed on 21-ft and 35-ft spectrographs with resolving powers up to 400,000. A complete rotational analysis could be made of the four strongest bands. A satisfactory vibrational analysis could also be made with the aid of fully deuterated diacetylene. The results indicate that the ``T” spectrum arises from transitions between two linear excited electronic states of the neutral diacetylene molecule, both of symmetry $^{1}{\it\Pi}$, whose geometries differ but little from that of $C_{4}H_{2}$ in the ground state. Similarly, the three totally symmetric normal modes of vibration of the lower of the two states have frequencies close to those of diacetylene in the ground state.
Description
$^{1}$H. Schuler, Spectrochimica Acta 4:85 (1950) $^{2}$H. Schuler and L. Reinebeck, Z. Naturf. 7a:285 (1952). $^{3}$H. Schuler and L. Reinebeck, Z. Naturf. 9a:350 (1954)
Author Institution: Division of Physics, National Research Council
Author Institution: Division of Physics, National Research Council