Fourier transforms modes

H-NMR studies were performed on a Bruker MSL-400 spectrometer operating in the Fourier transform mode, using a static multinuclei probehead operating at 400.13 MEtz. A pulse length of 1 iis is used for the 90° flip angle and the repetition time used (1 second) is longer than five times Tjz ( H) of the analyzed samples. 

NMR spectroscopy was performed with a Bruker AC-300 spectrometer at 75 MHz in the Fourier-transform mode, with proton decoupling at 30 C, using 5 mm tubes and D2O as solvent. The spectral width was 200 ppm. Chemical shifts are expressed in ppm relative to the resonance of external DSS (sodiiun 4,4-dimethyl-4-silapentane-1 -sulfonate). 

NMR spectra were obtained in continuous wave mode on a Varian T-60, and in the pulsed Fourier transform mode on a Varian HR-220 with Nicolet TT-100 Fourier transform accessory, a Nicolet NT-300 wide bore system, and a Bruker WM-500. 13C T1 data were obtained... 

The 500-MHz, H-n.m.r. spectra were recorded with a Bruker WM-500 spectrometer operating in the pulsed, Fourier-transform mode and equipped with a Bruker Aspect2000 computer having an 80k memory-capacity. The D resonance of D20 was used as the field-frequency lock-signal. The spectra were obtained by using a 90° pulse-width, and accumulated into 16k addresses with an acquisition time of... 

Surface science that is carried out under clean, ultrahigh-vacuum conditions utilizes with advantage the high resolution electron energy loss spectroscopy (HR EELS) that excels with its high sensitivity, but this technique does not match the energy resolution of IR or Raman spectroscopies. For adsorbates on real catalysts, therefore, the long time used IR spectroscopy, nowadays practiced almost exclusively in its Fourier transform mode (FTIR), is still the method of choice. 

Carbon-13 NMR spectra were obtained using a Varian XL-200 spectrometer operating in the Fourier transform mode. Polymer samples were run as gels or slurries in benzene-d, unless otherwise noted. Operating and processing conditions were standard for all polymer samples. Chemical shifts are reported relative to tetramethylsilane in ppm (6). 

Carbon 13 NMR spectra were obtained using a JEOL GX-500 spectrometer with a quadruture detection operating at a frequency of 125.77 MHz in a pulse-Fourier transform mode. FID s were acquired with a 16 bit A/D converter and stored on 32 or 64 K memory locations with 32 bit word length. The chemical shift was measured from an internal standard, hexamethyldisiloxane, which was taken as 2.03 ppm from tetramethylsilane(TMS). Internal lock was provided by an addition of benzene-dg. 

NMR spectra were recorded for an 8.06 wt % D2O solution at 62.89 MHz and ambient temperature on a Bruker WM 250 spectrometer operating at 5.87 T in the pulsed Fourier transform mode with inverse-gated decoupling. The pulse width and acquisition time were 30.5 ms and 0.442 s, respectively. Each spectrum contained 16,000 data points over a frequency of 18,518 Hz with about 2000 acquisitions. 

Carbon-13 NMR spectroscopy. Natural abundance carbon-13 NMR spectra were taken on a Varian XL-100 spectrometer operated in the Fourier transform mode at a frequency of 25.2 MHz. Samples of phosphogalactomannan were usually in excess of 100 mg ml of H20. The field was locked on the deuterium signal and the spectra were recorded with proton noise decoupled. Chemical shifts are reported in ppm from an external reference solution of 5% sodium (trimethylsilyl)-1-propane sulfonate (TSP) in a coaxial tube. The spectrum shown represents data from 64,000 transients. 

NMR spectra were recorded 270 MHz in the Fourier transform mode using systems described elsewhere (Lee and Sanaa, 1976). The spectra were analysed by LACON III. The coupling constant data were translated into conformational parameters using equations developed by Lee and Sanaa (1976) and the data are summarised in Table 1,... 

N.J., USA) as a lyophylized powder and used without further purification. 1% NMR spectra were recorded on a Bruker HFX-90 hlgh-resolution spectrometer ( % resonance frequency 9.12 MHz). (The Instrument was equipped with a Bruker Fast Fourier transform unit, a Nlcolet 1o8o data hemdling system, a Bruker B-SV 2 proton decoupler, and a.Bruker deuterium lock system.) The probe was kept at 43 - 2°c with a flow of temperature controlled air (Bruker temperature control unit B-ST 1oo/7oo). Field frequency lock was obtained from D2O In a 2 mm capillary Inserted into the I0- or 15-mm sample tube. 27.36 MHz I NMR spectra of the rlbonuclease-nucleotlde complexes were recorded on a Bruker WH-27o spectrometer In the Fourier transform mode. The chemical shift data cure given In ppm relative to the external stemdard (4 M solution of 95%-enriched I5NH4NO3 In 2 M HNO3). 

All H spectra were recorded In 5 irm-tubes on a Varlan XL-100-12 spectrometer operating In the Fourier transform mode at 100.06 MHz and locked to the deuterium resonance of the solvent, deuterium oxide. 

The NMR spectra were recorded on a Varian SC-300 spectrometer in Fourier transform mode at 300 MHz. When measured in H2O solution, the intensity of the solvent line was reduced by irradiation of water signal for 2s prior to the observation pulse. The pH measurements were carried out directly in the 5 mm o.d. NMR tubes using a 180-mm Ingold 405 M3 combination microelectrode. For D2O solutions the values used are the direct reading of digital pH meter (Orion Research Model 601). For analysis of the experimental pH dependence of the chemical shifts an iterative curve-fitting software was used. 

In most cases, the NMR spectrum will be acquired via the Fourier transform mode, and the following paragraph summarizes the basic concepts which will be used throughout. 

Infrared spectroscopy is predominantly performed in the Fourier-transform mode and then commonly abbreviated as FTIR. The great advantage of FTIR spectroscopy is the great number of measurement options (and accessories), that allow spectra to be taken conveniently from just about any kind of sample. Polymeric powders can be characterized by pressing them into the conventional KBr pellets, but also, without any sample preparation, by diffuse reflectance (DRIFT). Very thin films of polymers can be measured in the conventional transmission mode, but any kind of film (thick or thin), as well as large polymeric objects, can be measured by ATR. ATR probes can also be used to characterize solutions... 

Another relatively new device known as the ion cyclotron system, which is not a double-focusing system, can provide resolution to well over 100,000 and can operate in a Fourier transform mode, offering speed and sensitivity. 

Fig. 1. High-resolution spectrum of ATP. (a) 1959 Single-scan, 24.3-MHz, 5-mm tube, continuous-wave operation of a Varian 4302 dual-purpose NMR spectrometer. [ATP] = 500 mM. (b) 1976 10 scans, 72.9 MHz, 20-mm tube, in the Fourier-transform mode of operation, 20-sec repetition rate, and proton decoupling on a Bruker WH 180 NMR spectrometer. [ATP] = 1 mM. From Cohn (1979).

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