Broadband channel

RF channel. The portion of the instrument devoted to generating RF with a specific frequency. There are four types of RF channels that may be found in an NMR instrument a highband channel (for H and % and maybe H), a broadband channel, for all nuclides with Larmor frequencies at that of and lower, a lock channel (devoted exclusively H), and a fullband channel (any nucleus). Most instruments have one of the first three channels listed above. 

Broadband channel. The portion of a spectrometer capable of generating RF to excite nuclei with Larmor frequencies less than or equal to that of P (at 40% of the H Larmor frequency). In some cases, the broadband channel may be capable of exciting ° TI (at 57% of the H Larmor frequency). The preamplifier in the broadband channel s receiver will normally feature a low-pass filter and a bandstop (notch reject) filter. 

HMBC-based experiments). From the 2D spectrum it was possible to directly assign the platinum resonances of the different isomers and hence determine the isomer ratios. These data were collected on a triple-channel instrument equipped with a Broadband probe for which the broadbanded channel had been tuned to Pt. 

The Viking Orbiters carried an Infrared Thermal Mapper (IRTM) with broadband channels centered at 7, 9,11,15, and 20 /xm, as well as one channel covering the visible and near infrared (0.3 to 3 /xm), designed to measure the albedo. A description of the instrument and scientific results have been published by Chase et al. (1978) and by Kieffer et al. (1977). Christensen (1998) compared the results of the Viking IRTM and the Mariner 9 IRIS in order to gain information on the... 

The overall OD vibrational distribution from the HOD photodissociation resembles that from the D2O photodissociation. Similarly, the OH vibrational distribution from the HOD photodissociation is similar to that from the H2O photodissociation. There are, however, notable differences for the OD products from HOD and D2O, similarly for the OH products from HOD and H2O. It is also clear that rotational temperatures are all quite cold for all OH (OD) products. From the above experimental results, the branching ratio of the H and D product channels from the HOD photodissociation can be estimated, since the mixed sample of H2O and D2O with 1 1 ratio can quickly reach equilibrium with the exact ratios of H2O, HOD and D2O known to be 1 2 1. Because the absorption spectrum of H2O at 157nm is a broadband transition, we can reasonably assume that the absorption cross-sections are the same for the three water isotopomer molecules. It is also quite obvious that the quantum yield of these molecules at 157 nm excitation should be unity since the A1B surface is purely repulsive and is not coupled to any other electronic surfaces. From the above measurement of the H-atom products from the mixed sample, the ratio of the H-atom products from HOD and H2O is determined to be 1.27. If we assume the quantum yield for H2O at 157 is unity, the quantum yield for the H production should be 0.64 (i.e. 1.27 divided by 2) since the HOD concentration is twice that of H2O in the mixed sample. Similarly, from the above measurement of the D-atom product from the mixed sample, we can actually determine the ratio of the D-atom products from HOD and D2O to be 0.52. Using the same assumption that the quantum yield of the D2O photodissociation at 157 nm is unity, the quantum yield of the D-atom production from the HOD photodissociation at 157 nm is determined to be 0.26. Therefore the total quantum yield for the H and D products from HOD is 0.64 + 0.26 = 0.90. This is a little bit smaller ( 10%) than 1 since the total quantum yield of the H and D productions from the HOD photodissociation should be unity because no other dissociation channel is present for the HOD photodissociation other than the H and D atom elimination processes. There are a couple of sources of error, however, in this estimation (a) the assumption that the absorption cross-sections of all three water isotopomers at 157 nm are exactly the same, and (b) the accuracy of the volume mixture in the... 

The basic components of the solid state spectrometer are the same as the solution-phase instrument data system, pulse programmer, observe and decoupler transmitters, magnetic system, and probes. In addition, high-power amplifiers are required for the two transmitters and a pneumatic spinning unit to achieve the necessary spin rates for MAS. Normally, the observe transmitter for 13C work requires broadband amplification of approximately 400 W of power for a 5.87-T, 250-MHz instrument. The amplifier should have triggering capabilities so that only the radiofrequency (rf) pulse is amplified. This will minimize noise contributions to the measured spectrum. So that the Hartmann-Hahn condition may be achieved, the decoupler amplifier must produce an rf signal at one-fourth the power level of the observe channel for carbon work. 

Fig. 33 Two-photon fluorescent images of photosensitive films developed (via 350-nm broadband exposure, 4.4mW/cm ) using an Air Force resolution target mask, a Image recorded by channel 1, b image recorded by channel 2, and c fluorescence intensity by scanning an xy line across one set of three-membered elements (line across set 5)...

The T, Inversion-Recovery experiment is not restricted to C nuclei, but may also be applied to other nuclei, e.g, protons. In this case, the pulse sequence for the observe channel is the same, but no broadband decoupling is used. 

The masking behavior of stereo signals is improved if a two-channel signal can be switched between left/right and sum/difference representation. Both broadband and critical band-wise switching has been proposed [Johnston, 1989a],... 

Clouds and the Earth s Radiant Energy System (CERES) CERES is a broadband three-channel scanning radiometer. One channel measures reflected solar radiation in the range 0.3 pm-5.0 pm. Two other channels (0.3 pm-100 pm and 8 pm-12 pm) measure reflected and emitted radiant energy at the top of the atmosphere. 

The c.w. dye laser can also be passively mode-locked and two different arrangements have been used. The first employed two free flowing dye streams, one for the laser dye and the other for the absorber (see Fig. 4) [18, 19]. In the alternative arrangement, the saturable absorber dye flows in a narrow channel of variable thickness (0.2—0.5mm) and in contact with a 100% broadband reflectivity mirror. With an absorber thickness of 0.5 mm, output pulses of 1 ps duration have been obtained [20]. Pulses as short as 0.3ps were produced when the DODCI cell length was shortened to 0.2 mm. The subpicosecond pulses produced in this arrangement were transform-limited in bandwidth. 

Connecting terminals to hosts appears to be the most widely used area for broadband. Allows the same channel to carry voice and video signals. The signal rates for broadband are not impressive for data communications at this time under 1 million bits per second for most applications ... 

For HMQC spectroscopy in which both the detector I and indirect S nuclei are heteronuclei , a third spectrometer channel is required. An inverse broadband, triple resonance probe head in which the inner coil is tuned to H, I and lock, and the outer coil is broadbanded is then the best option, particularly where a single / nuclide or H will be used for detection. Such probe heads are stock items for some manufacturers (Bruker). Although it may be possible to build probe heads in which two channels are broadbanded, the lead time on such a probe head is likely to be long, and the performance markedly inferior due to the technical difficulties involved. 

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