Ultrahigh spectral resolution

Saturation spectroscopy makes it possible to attain very high spectral resolution by means of ultranarrow spectral saturation resonances whose width is five to six orders of magnitude smaller than the Doppler width. Tunable lasers capable of an emission 

1 Ultranarrow spectral resonances and ultrastable-frequency lasers 

2 Ultrahigh-resolution saturation spectroscopy based on selection of slow molecules 

One should then operate with low light intensities that cause no saturation of the absorption by molecules with the mean thermal velocity vq. Of course, use should be made of high-sensitivity methods for detecting ultranarrow resonance signals. The intensity of such signals is very low because of the need to use low-pressure gases (at some Torr) to reduce collisional broadening, and the small proportion of 

Saturation spectroscopy with selection of ultraslow molecules is a unique method for studying rotational-vibrational transitions in polyatomic molecules, with a spectral resolution of Av/vq = 10 -10 . A spectral resolution as high as this is necessary in investigations into the fundamental effect of parity violation in chiral molecules. 

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H. Qiao, X. Zhang, X.-H. Zhu, F. Du and W. Chen, In vivo P MRS of human brain at high/ultrahigh fields a quantitative comparison of NMR detection sensitivity and spectral resolution between 4 T and 7 T. Magn. Reson. Imaging, 2006,24,1281-1286. 

Significantly improved spectral resolution of CP MAS NMR spectra of chlorinated, brominated and iodinated sohd organic compounds when such spectra are recorded at ultrahigh magnetic field strengths (21.1 T). ... 

Hockaday, W. C., Grannas, A. M., Kim, S., and Hatcher, P. G. (2006). Direct molecular evidence for the degradation and mobility of black carbon in soils from ultrahigh-resolution mass spectral analysis of dissolved organic matter from a fire-impacted forest soil. Org. Geochem. 37, 501-510. 

Figure 3. W-Band (94.9 GHz) EPR spectra of human Hb(NO>4at sample temperatures ranging from 7 to 200 K. The spectra were obtained in CW mode with fieid moduiation of iO G amplitude at a frequency of 100 kHz. Hb(NO)4 was prepared by reaction of a phosphate-buffered (pH 7.4) saline solution of Hb A (deoxygenated with ultrahigh-puiity argon) with a deoxygenated aqueous solution of sodium nitrite (preceded by addition of sodium dithio-nite) excess reagents were removed by G-25 chromatography. For certain spectral features, highlighted with the shaded lines, the W-band spectra show a notable increase in resolution of temperature-dependent lineshape changes as compared to X- and Q-band spectra. EPR spectra exhibit both axial and rhombic spectral components in equilibrium that favors the axial components with increasing temperature.

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