Frequency comb-referenced measurements of sub-Doppler laser saturation dip absorption lines in the $v_1$ + $v_3$ band of acetylene near 1.5 μm 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.

中文翻译：

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C2H2的v1 + v3频段的频率测量和亚多普勒跳变的自扩展

子波中亚多普勒饱和吸收吸收谱线的频率梳参考测量 $v_{\mathrm{1个}}$ + $v_3$乙炔的谱带接近1.5μm被报告。这些测量包括的跃迁涉及比该频段先前测量的频率更高的旋转水平。测量频率的精度通常优于10 kHz。测量所观察到的亚多普勒谱线宽度随压力变化的结果表明，自压力展宽系数比不饱和多普勒极限谱的常规压力展宽所获得的系数大约3.5倍。这归因于在低压子多普勒测量中速度变化的碰撞对总相移速率的贡献。在较高的压力下，当每次弹性碰撞的均匀展宽变得可与典型的多普勒频移相媲美时，速度变化的碰撞就不再对增量压力展宽做出重大贡献。