Similarity results for operators of class C₀

If T is a multiplicity-free contraction of class C_0 with minimal function m_T, then it is quasisimilar to the Jordan block S(m_T). In case m_T is a Blaschke product with simple roots forming a Carleson sequence, we show that the relation between T and S(m_T) can be strengthened to similarity. Under the additional assumption that u(T) has closed range for every inner divisor u of m_T, the result also holds in the more general setting where the roots have bounded multiplicities.