Referencing spectra

Proton-decoupled P spectrum, referenced to 85% aqueous H3PO4 at 291K. The linear increase of the P NMR shift for PH3 in various solvents (CCI4, benzene, toluene, and cyclohexane) with increasing temperature (30 to 90°C) is illustrated in the paper [8]. J(P-H) was taken from [12]. 

Figure Bl.11.9. Integrated 250 MHz H NMR spectrum of dilute propan-1-ol in dinrethylsulfoxide solvent. Here, the shift order parallels the chemical order. Arr expansion of the H2-I nrultiplet is included, as is the implicit frequency scale, also referenced here to TMS = 0.

The neutron dose to graphite due to irradiation is commonly reported as a time integrated flux of neutrons per unit area (or fluence) referenced to a particular neutron energy. Neutron energies greater that 50 keV, 0.1 MeV, 0.18 MeV, and 1 MeV were adopted in the past and can be readily foimd in the literature. In the U.K., irradiation data are frequently reported in fluences referenced to a standard flux spectrum at a particular point in the DIDO reactor, for which the displacement rate was measured by the nickel activation [ Ni(np) t o] reaction [equivalent DIDO nickel (EDN)]. Early on, neutron irradiation doses to the graphite moderator were reported in terms of the bum-up (energy extracted) from imit mass of the adjacent nuclear fuel, i.e., MW days per adjacent tonne of fuel, or MWd/Ate. 

Figure 5-3. UPS spectrum of Au illustrating the procedure to obtain vacuum level referenced spectra.

Figure 3.18 Spectrum of free energies of hydrogen adsorption, AGh, on binary surface alloys at r = 298K. The vertical axis shows the number of elements with free energies within 0.1 eV windows (O.O-O.l eV, 0.1-0.2 eV, etc.). The sohd vertical line indicates AGh = 0- The dashed vertical line gives the hydrogen free energy adsorption for pure Pt. AU free energies are referenced to gas phase H2. Adapted from [Greeley and Nprskov, 2007] see this reference for more details.

For a comparison of experimental Mossbauer isomer shifts, the values have to be referenced to a common standard. According to (4.23), the results of a measurement depend on the type of source material, for example, Co diffused into rhodium, palladium, platinum, or other metals. For Fe Mossbauer spectroscopy, the spectrometer is usually calibrated by using the known absorption spectrum of metallic iron (a-phase). Therefore, Fe isomer shifts are commonly reported relative to the centroid of the magnetically split spectrum of a-iron (Sect. 3.1.3). Conversion factors for sodium nitroprusside dihydrate, Na2[Fe(CN)5N0]-2H20, or sodium ferrocyanide, Na4[Fe(CN)]6, which have also been used as reference materials, are found in Table 3.1. Reference materials for other isotopes are given in Table 1.3 of [18] in Chap. 1. 

One of the resulting 129Xe NMR spectra is shown in Figure 5.3.8 (solid line 2) in comparison with the spectrum of the same initial mixture without combustion (dashed line 1). Referenced with 0 ppm is the gas phase peak at room temperature. 

Using the techniques referenced in Section 5.2, a detailed list of potential accident scenarios can be prepared. This list can then be refined to give the minimum number of scenarios that need to be assessed to adequately reflect the spectrum of possible incidents and to satisfy the requirements of the study. The steps involved may include ... 

In order to have a reliable measure of chemical shift, we need to have a reference for the value. In proton NMR this is normally referenced to tetramethyl silane (TMS) which is notionally given a chemical shift of zero. Spectrum 1.1 shows what a spectrum of TMS would look like. 

Finally, it has been noted that some people think that they need TMS in their samples to enable them to lock. This is not the case On modem spectrometers, TMS is used for referencing only. There was a time when it was used for locking CW instruments (in an early form of spectrum averaging) but it is not used in that way for FT instruments now. 

The proton NMR spectrum of miconazole nitrate was obtained using a Bruker Instrument operating at 300, 400, or 500 MHz. Standard Bruker Software was used to execute the recording of DEPT, COSY, and HETCOR spectra. The sample was dissolved in DMSO-d6 and all resonance bands were referenced to the tetramethyl-silane (TMS) internal standard. The 1H NMR spectra of miconazole nitrate are shown in Figs. 5-7 and the COSY 1H NMR spectrum is shown in Fig. 8. The H NMR assignments for miconazole nitrate are provided in Table 3. 

Figure 7. 31P-CP/MAS solid-state spectrum of [PtCl2(PPhgCHs)t] at 36,442 MHz (a), 31P-CP/MAS solid-state spectrum of [PtCl2(PPh2CH2CH2Si(OEt)s] at 36.442 MHz (b), and 31P-CP/MAS solid-state spectrum of PtCl2[PPh2CH2CHgSi-(OEt)s] covalently immobilized on glass beads. All spectra referenced to external 85% HsPOk (18,). (Reproduced with permission from Ref. 40. Copyright 1982, Royal Society of London.)...

Fig. 10 Electrochemical energy level model for orbital mediated tunneling. Ap and Ac are the gas-and crystalline-phase electron affinities, 1/2(SCE) is the electrochemical potential referenced to the saturated calomel electrode, and provides the solution-phase electron affinity. Ev, is the Fermi level of the substrate (Au here). The corresponding positions in the OMT spectrum are shown by Ar and A0 and correspond to the electron affinity and ionization potential of the adsorbate film modified by interaction with the supporting metal, At. The spectrum is that of nickel(II) tetraphenyl-porphyrin on Au (111). (Reprinted with permission from [26])...

The l3C nmr spectrum reproduced in Figure 3 was obtained from a D20/Na0D solution of calcium leucovorin on a Varian XL100 Spectrometer. The assignments on the TMS scale and referenced to dioxane are listed below ... 

Fig. 1. He(I) P.E. spectrum of benzene (6). Like all other figures of this review, the spectrum is adapted from the referenced) quoted in parentheses...

Figure 3. lH NMR spectrum of 14, Z-H, in S02CIF, referenced to external TMS (Reproducedfrom reference 38. Copyright 2006 American Chemical Society.)... 

Fitting of these curves yields the sum of the dipolar coupling plus the /-coupling. Referencing to a spectrum without alignment allows extraction of the dipolar coupling constant. 

It is technically possible, but very difficult, to measure the exact frequency of a radio signal, and in practice the frequency of the energy absorbed by a test compound (usually called the resonance frequency) is measured relative to that of a reference compound. This reference may be mixed with the sample (direct referencing), or if contamination of the sample is undesirable it may be placed in a separate container within the sample tube (external referencing). In proton and 13C NMR, the reference compound usually used is TMS (tetra-methyl silane) or its water-soluble derivative DSS (2,2-dimethylsilapentane 5-sulphonic acid). These compounds give a sharp proton peak at the right-hand side of a typical NMR spectrum (Figure 2.39). 

Figure 4 Detail of the amide carbonyl resonances in the C-NMR spectrum (100 MHz) of poly (Lys-25) in 70% H2O/30% D2O solution. The spectrum was recorded on a Varian INOVA 400 NMR spectrometer. Chemical shifts were referenced to external tetramethylsilane.

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