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Phase Analysis of Vibrational Wavepackets in the Ground and the Excited States in Polydiacetylene
Takayoshi Kobayashi and Mitsuhiro Ikuta

Molecular vibration of several modes in blue-phase polydiacetylene-3- butoxycarbonylmethylurethane (PDA-3BCMU) was real-time observed by 5-fs pump-probe measurement. The contribution of the vibrational wavepackets in the ground state and in the excited state in the signal were separated by multichannel measurement. The C=C stretching mode in the ground state starts to oscillate p-out-of-phase with the CºC stretching mode. The structure of PDA-3BCMU in the geometrically relaxed state is not pure butatriene-type but more like acetylene-type. The frequencies of C=C and CºC stretching modes there were determined by singular value decomposition method to be 1472 ± 6 cm-1 and 2092 ± 6 cm-1, respectively. The double and triple bond stretching frequencies in the ground state were deter-mined to be 1463 ± 6 cm-1 and 2083 ± 6 cm-1, respectively.

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