Spectroscopy of Carbon Vapor Condensed in Rare-Gas Matrices at 4° and 20°K. II

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Abstract
The vaporization of C13‐substituted carbon has established the isolation of C3 molecules in the matrix and the assignment of the v 3″ frequency observed in the infrared spectrum. A vibrational analysis of the near‐ultraviolet spectrum (the well‐known 4050‐Å gas bands) of C3 trapped in a neon or argon matrix has been carried out. The presence of a large Renner effect (ε=+0.566) in the bending motion in the excited state of this 1Π u ↔X 1Σ g + transition has been confirmed. Infrared and fluorescence spectra also support the assignment of a low bending frequency (∼70 cm—1) in the ground state as recently proposed by Gausset, Herzberg, Lagerqvist, and Rosen. Then the following vibrational frequencies apply: 1 Π u state : ν 1 ′ =1125 cm −1 , ν 2 ′ =305 cm −1 , ν 3 ′ =?; 1 Σ g + ground state : ν 1 ′′ =1235 cm −1 , ν 2 ′′ ≅70 cm −1 (?), ν 3 ′′ =2040 cm −1 . v 2″ is still doubtful because it does not yield thermodynamic functions for C3 which agree with those derived by mass spectrometry. The f number (oscillator strength) of the 0–0 band has been found to be about 7×10—4 in a neon matrix. The properties of a long‐lived emission (lifetime=0.02 sec in neon) at 5856 Å indicate that it is the 3Π u →1Σ g + transition of C3. Another, rather unpredictable, system of bands near 4200 Å has also been seen in absorption and emission, but the molecule producing these bands has not been identified. An attempt has been made, via a linear chain model, to assign the stretching frequencies of the larger carbon molecules, C4, ···, C12, which have been observed in the infrared after solid‐state diffusion was allowed to occur.

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