Stepwise Two-Photon Excitation into Excitonic Molecule via Exciton State of Large Wave Vectors in CuCl

By the use of two dye lasers, the spatial dispersion of the excitonic molecule has been studied by the excitation into states of large wave vectors. With the first laser beam ω 1 ( k 1 ) an excitonic polariton is created at a large wave vector and an excitonic molecule is formed with the second laser beam ω 2 ( k 2 ). The relation between ω 1 and ω 2 is expressed by a straight line of slope 0.57, and the mass of the excitonic molecule is determined to be 2.3 times as much as that of the transverse exciton. In the two different configurations in which the two laser beams are in the same and opposite directions, excitonic molecules are created at k 1 ± k 2 . From the analysis of the relation between ω 1 and ω 2 in the two configurations, the excitonic mass is deduced to be (2.5∼3.0) m 0 .