C $_2$ H $_2$的$v_1+v_3$带亚多普勒跃迁的频率测量和自展宽
Frequency measurements and self-broadening of sub-Doppler transitions in the $v_1+v_3$ band of C$_2$H$_2$
摘要：
本文报道了用频率梳参考法测量乙炔在$1.5\,μ\mathrm{m}$附近的$v_1+v_3$带的亚多普勒激光饱和吸收线。这些测量包括涉及比先前在该频带中测量的频率更高的旋转能级的跃迁。测量频率的精度通常优于10 kHz。作为压力的函数的所观察到的亚多普勒线宽的测量表明，自压力加宽系数是约3.5倍，大于来自传统的压力加宽的不饱和多普勒限制光谱。这是由于在低压亚多普勒测量中，速度变化碰撞对总退相速率的贡献。在较高压力下，当均匀加宽变得与每次弹性碰撞的典型多普勒频移相当时，速度变化碰撞不再对增量压力加宽有显著贡献。本文发展了一个含时软碰撞模型来描述亚多普勒压力展宽在低压区和高压区之间的转变。
英文摘要：
Frequency comb-referenced measurements of sub-Doppler laser saturation dip absorption lines in the $v_1+v_3$ band of acetylene near $1.5\,μ\mathrm{m}$ are reported. These measurements include transitions involving higher rotational levels than previously frequency measured in this band. The accuracy of the measured frequencies is typically better than 10 kHz. Measurements of the observed sub-Doppler line widths as a function of pressure showed that the self pressure-broadening coefficients are about 3.5 times larger than those derived from conventional pressure broadening of unsaturated Doppler-limited spectra. This is attributed to the contribution of velocity-changing collisions to the total dephasing rate in the low pressure sub-Doppler measurements. At higher pressures, when the homogeneous broadening becomes comparable to the typical Doppler shift per elastic collision, the velocity changing collisions cease to contribute significantly to the incremental pressure broadening. A time-dependent soft collision model is developed to illustrate the transition between low and high pressure regimes of sub-Doppler pressure-broadening.
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