Abstract: The Raman-coupled interaction between an atom and a single mode of a cavity field is studied. For the cases in which a light field is initially in a coherent state and in a thermal state separately, we have derived the analytic expressions for the time evolutions of atomic population difference $W$, modulus $B$ of the Bloch vector, and entropy $E$. We find that the time evolutions of these quantities are periodic with a period of $\pi $. The maxima of $W$ and $B$ appear at the scaled interaction time points $\tau = k\pi (k = 0,1,2,\ldots)$. At these time points, $E = 0$, which shows that the atom and the field are not entangled. Between these time points, $E \ne 0$, which means that the atom and the field are entangled. When the field is initially in a coherent state, near the maxima, the envelope of $W$ is a Gaussian function with a variance of $1 /{\left( {4\bar {n}} \right)}$ ($\bar {n}$ is the mean number of photons). Under the envelope, $W$ oscillates at a frequency of $\bar {n} / \pi $. When the field is initially in a thermal state, near the maxima, $W$ is a Lorentz function with a width of $1/ \bar {n}$.

Key words: Raman-coupled model, atomic dynamics, entropy, entanglement