For electromagnetic pulses without a carrier frequency, propagating in a system of multilevel atoms with a fast irreversible relaxation of the induced dipole moment, but a slow relaxation of the populations of quantum states, the nonlinear integro-differential equations of the ‘reaction–diffusion’ type are derived. One-dimensional soliton-like solutions of these equations in the form of unipolar pulses are found and analyzed. It is shown that such pulses can be formed in a nonequilibrium medium. These pulses transfer a medium to other metastable states, which depend on the input conditions. The propagation of these soliton-like signals is accompanied by a change in the populations of quantum states of atoms in the modes of switching waves with the memory of input conditions.

对于没有载波频率的电磁脉冲，在多能级原子系统中传播，诱导偶极矩快速不可逆弛豫，但量子态群缓慢弛豫，“反应 - 扩散”的非线性积分微分方程类型是派生的。找到并分析了这些方程的单极脉冲形式的一维孤子样解。结果表明，这种脉冲可以在非平衡介质中形成。这些脉冲将介质转换为其他亚稳态，这取决于输入条件。这些类孤子信号的传播伴随着具有输入条件记忆的开关波模式中原子量子态种群的变化。