Energy transfer in a pulsed-microwave enhanced flame is investigated using hybrid fs/ps coherent anti-Stokes Raman scattering (CARS) to monitor both vibrational and rotational temperatures of nitrogen in an atmospheric pressure laminar premixed natural gas/air stagnation flame. Temperatures were measured throughout the laminar flame structure following a 30-kW peak power, 2 $\mu$s duration, 3 GHz microwave pulse in a resonant waveguide cavity. CARS measurements show a delayed increase in vibrational temperature, indicating energy loading via electron impact and subsequent energy cascade. Vibrational energy thermalization was observed over timescales faster than transport through the flame zone, but slower than predicted by known vibrational-translational rates, suggesting a long-lived pathway for increased vibrational temperature. Peak vibrational temperature increases of 100 K were observed and thermalize over 100${}^{\prime }$s of microseconds, resulting in a measurable increase in the rotational temperature over the same time interval. The magnitude of vibrational excitation and rate of thermalization in such plasma-assisted combustion environments is critical for applications including combustion ignition and control, and hybrid fs/ps CARS measurements provide the necessary detail on vibrational-translational relaxation processes of ground state nitrogen.

使用混合fs / ps相干反斯托克斯拉曼散射（CARS）研究了大气压层流预混天然气/空气停滞火焰中氮气的振动和旋转温度，研究了脉冲微波增强火焰中的能量转移。在30 kW峰值功率2下，测量整个层流火焰结构的温度2$\mu$在谐振波导腔中的持续时间为3 GHz微波脉冲。CARS测量显示振动温度的延迟增加，表明通过电子撞击和随后的能量级联来加载能量。在时间尺度上观察到振动能量热化比通过火焰区域的传输快，但比已知的振动平移速率所预测的要慢，这表明增加振动温度是一条长寿的途径。观察到峰值振动温度升高100 K，并在超过100 K的温度下热化${}^{\prime }$秒的微秒，导致同一时间间隔内旋转温度的可测量升高。在这种等离子辅助燃烧环境中，振动激发的幅度和热化率对于包括燃烧点火和控制在内的应用至关重要，混合fs / ps CARS测量提供了基态氮振动-平移弛豫过程的必要细节。