High resolution study of the ν1 vibration of CH3 by coherent Raman photofragment spectroscopy

摘要: Coherent anti‐Stokes Raman spectroscopy (CARS) was used to measure the vibrational–rotational Q‐branch structure of ν1 symmetric stretch methyl radicals produced by 266 nm laser photolysis iodide. Spectra were recorded in both flow cells and free jet expansions at instrumental resolutions ranging from 0.25 0.005 cm−1. Due high recoil velocity CH3 fragment, Doppler collisional broadening transitions is appreciable. Even highest resolution such leads interference effects among closely spaced that influence line positions intensities observed CARS spectra. The molecular parameters (cm−1) obtained analysis are ν1=3004.42(4), αB1=0.0851(8), αC1=0.0475(7), DN1−DN0=−0.000 046(8), DNK1−DNK0=0.000 083(20), and, with assumptions, DK1−DK0=−0.000 039. These results infrared data literature yield a CH bond length 1.08378(5) A for (1000) state some assumptio...