Structural information on a hydrogen-bonded polymer from nonlinear infrared spectroscopy

Transient infrared hole burning with intense picosecond pulses is applied to a detailed study of the spectral inhomogeneity of the OH stretching band of poly(vinylbutanal) at 293 K. The frequency dependencies of the quasi-homogeneous line width Γ(ν₀) and the peak absorption cross section σ(ν₀) are measured. By use of these results and a semiempirical potential model for the hydrogen bonds (OH⋯O), a simple Gaussian distribution of oxygen-oxygen distances is shown to account for the conventional (asymmetric) absorption band. The corresponding spectral number density is also determined with asymmetric shape and a blue shift of 40 cm^-1.