We uncover a highly nontrivial dependence of the spin-noise (SN) resonance broadening induced by the intense probe beam. The measurements were performed by probing the cell with cesium vapor at the wavelengths of the transition $6{}^{2}S_{1/2}\leftrightarrow 6{}^{2}P_{3/2}$ ($D_2$ line) with the unresolved hyperfine structure of the excited state. The light-induced broadening of the SN resonance was found to differ strongly at different slopes of the $D_2$ line and, generally, varied nonmonotonically with light power. We discuss the effect in terms of the phenomenological Bloch equations for the spin fluctuations and demonstrate that the SN broadening behavior strongly depends on the relation between the pumping and excited-level decay rates, the spin precession, and decoherence rates. To reconcile the puzzling experimental results, we propose that the degree of optical perturbation of the spin system is controlled by the route of the excited-state relaxation of the atom or, in other words, that the act of optical excitation of the atom does not necessarily break down completely its ground-state coherence and continuity of the spin precession. Spectral asymmetry of the effect, in this case, is provided by the position of the “closed” transition $F=4\leftrightarrow F^{\prime }=5$ at the short-wavelength side of the line. This hypothesis, however, remains to be proven by microscopic calculations.

中文翻译：

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异常光诱导铯蒸气中自旋噪声共振的加宽

我们发现强烈探测光束引起的自旋噪声（SN）共振加宽的高度非平凡的依赖性。通过在过渡波长处用铯蒸气探测电池来进行测量$6{}^{\mathrm{2个}}\mathrm{小号}_{\mathrm{1个}/\mathrm{2个}}\leftrightarrow 6{}^{\mathrm{2个}}P_{3/\mathrm{2个}}$ （$d_{\mathrm{2个}}$线）具有未解析的激发态超细结构。发现在SN的不同斜率下，光诱导的SN共振展宽差异很大。$d_{\mathrm{2个}}$线，并且通常随光功率非单调变化。我们用现象学Bloch方程讨论自旋涨落的影响，并证明SN展宽行为强烈取决于泵浦和激发能级衰减率，自旋进动和退相干率之间的关系。为了使令人困惑的实验结果一致，我们提出，自旋系统的光学扰动程度是由原子的激发态弛豫的路径控制的，换句话说，原子的光学激发行为并不必须完全破坏其自旋进动的基态一致性和连续性。在这种情况下，效应的光谱不对称性由“闭合”过渡的位置提供$F=4\leftrightarrow F^{\prime }=5$在该线的短波长一侧。然而，这一假设仍有待通过微观计算加以证明。