  We develop a theoretical framework to understand the preparation and
relaxation of a metastable Mott insulator state within the first excited band
of a 1D optical lattice. The state is loaded by "lifting" atoms from the ground
to the first excited band by means of a stimulated Raman transition. We
determine the effect of pulse duration on the accuracy of the state preparation
for the case of a Gaussian pulse shape. Relaxation of the prepared state occurs
in two major stages: double-occupied sites occurring due to quantum
fluctuations initially lead to interband transitions followed by a spreading of
particles in the trap and thermalization. We find the characteristic relaxation
times at the earliest stage and at asymptotically long times approaching
equilibrium. Our theory is applicable to recent experiments performed with 1D
optical lattices [T. M\"uller, S. F\"olling, A. Widera, and I. Bloch, Phys.
Rev. Lett. \textbf{99}, 200405 (2007)].
