Unusual behavior of thermal lens in alcohols.

We use a femtosecond pump-probe Z-scan technique to measure the thermal lens (TL) signal in a homologous series of primary alcohols. The trend in these experimentally measured TL signals deviates in a counterintuitive manner from the ones calculated using theoretical models that are only based on the macroscopic parameters. Introspection shows that the present TL theories are based on heat conduction for low absorbing samples without considering any convective mode of heat transfer. Our studies on highly absorbing samples indicate the importance of convective mode of heat transfer in TL studies.