Peak matching mode

Finally, the instrument can be operated in the peak-matching mode, which provides optimum mass resolving power and mass accuracy. Here the magnetic field strength is kept constant and the electric sector and acceleration voltages are scanned over a relatively small m/z range. This mode of operation is suitable when two ions that are very close in mass need to be separated or when the elemental composition of a molecule is to be determined at high resolution. 

A mass accuracy better than 1 ppm is routinely obtained by the better instruments when they are operated in a peak matching mode. An interlaboratory study of mass accuracy of different instruments and operating modes can be found in Reference 231. 

Peak-Matching Mode Peak matching is a more accurate mass measurement technique (<0.3 ppm precision). Instead of acquiring the complete spectrum, the... 

FIG. 8. Phase-matching peaks for mode combination 12 observed with a sample 130 Mm thick. The peak at the lower temperature is generated by right circularly polarized fundamental waves and the one at the higher temperature by left circularly polarized fundamental waves. The solid line is the theoretical phase-matching curve and the dots are experimental data points. The uncertainty in the experimental third-harmonic intensity is about 20%. 

FIG. 9. Phase-matching peak for mode combination 2 observed with a sample 130 Mm thick. The circles are experimental points with an uncertainty of 20%. The curve is a smooth fit to the data. 

Spectra were acquired as the direct probe was heated over the range 50 - 300°C. Accurate mass measurements made by peak matching in either El or Cl mode (resolution M/dM about 10 000). 

Nevertheless, the avena coleoptile exhibits a curvature to unilateral UV-illumina-tion with a satisfactory log-linear response/time relationship38) (the bending mode is similar to that observed for the second positive curvature which develops from the coleoptile base cf. 2.2). Fig. 5 338) shows that the double-peaked action spectrum does not match neither flavin (Fig. 5 5,16S)) nor carotenoid absorption (Fig. 5 4,183)), most likely excluding both as photoreceptors. The growth hormone auxin (cf. 2.4 and Scheme 1) has been discussed to be a possible photoreceptor. However, in this case, this is not supported by the action spectrum either. 

We used short broadband pump pulses (spectral width 200 cm 1, pulse duration 130 fs FWHM) to excite impulsively the section of the NH absorption spectrum which includes the ffec-exciton peak and the first three satellite peaks [4], The transient absorbance change signal shows pronounced oscillations that persist up to about 15ps and contain two distinct frequency components whose temperature dependence and frequencies match perfectly with two phonon bands in the non-resonant electronic Raman spectrum of ACN [3] (Fig. 2a, b). Therefore the oscillations are assigned to the excitation of phonon wavepackets in the ground state. The corresponding excitation process is only possible if the phonon modes are coupled to the NH mode. Self trapping theory says that these are the phonon modes, which induce the self localization. 

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