  A new approach to the theory of atoms' interaction with chirped Raman pulses
is developed. When the pulses have sufficiently close effective wave lengths,
which are smaller than the atomic cloud size, equations for the family of the
matrix elements of the atomic density matrix in the Wigner representation are
derived. The solution, involving linear (in the pulse duration) phase
corrections, is obtained for the rectangular pulse. The interferometric part of
the atoms' excitation is calculated.
