Complex sentence: The model and the experiment lead to the prediction of "two" high energy α-particles of almost equal energy, one being the primary α-particle and the other a secondary α-particle, both emitted at an angle of 155 degrees.
Split into simpler sentences: The model and the experiment predicted "two" high energy α-particles of almost equal energy. One was the primary α-particle and the other a secondary α-particle, both emitted at an angle of 155 degrees.