| Abstract: | Spectra of acetylene dimers and trimers containing one or more C2D2 monomer are studied in the ν3 fundamental band region of C2D2 (≈2440?cm?1) using a tuneable infrared diode laser to probe a pulsed supersonic slit jet expansion. Four new subbands are observed in the perpendicular band of (C2D2)2, and this enables the first direct determination of the A rotational constant for an acetylene dimer. The value found for A is significantly larger than the previous indirect value based on microwave spectra. The dimer parallel band is observed and found to be highly perturbed, and observations are extended for the mixed dimer C2D2 – C2H2. The trimers (C2D2)3, (C2D2)2 – C2H2, and C2D2 – (C2H2)2 are observed spectroscopically for the first time. Establishment of a precise band origin is difficult for (C2D2)3 because of the inherent nature of the spectrum, but this is possible for two out of three of the bands of the mixed trimers. |
