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Hi.We have a 500MHz BRUKER AVANCE spectrometer.unfortunately its has been quenched.we have 3 probes:5mmQNP , 5mmBBI and 10mm.Can we run NQR test with this machine?if yes,please tell me how can we do it?

asked May 26 '13 at 05:28

shokoufeh%20karimnia's gravatar image

shokoufeh karimnia
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First, you have to identify the sample and nuclei, which has a 500 MHz torsional frequency. Try to look for the signal by slowly changing the frequency.

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answered May 26 '13 at 22:56

Mallikarjun's gravatar image

Mallikarjun
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It is possible, but inconvenient (not easy).

You could observe NQR with the BB (broadband) channel of any probe. BBI or BBO certainly. I am not sure if QNP has a broadband channel.

It is inconvenient because you may have to search over a very wide frequency range, which requires changing the spectrometer frequency SFO1 (or combination of O1 plus BF1) in steps of perhaps 50 kHz, and re-tuning the probe as needed.

Before you get started, you should find out the approximate frequency range for a nucleus of interest. For example, I searched via Google for "chlorine nqr frequency" and found a chapter about NQR in "Applications of Physical Methods to Inorganic and Bioinorganic Chemistry," edited by Robert A. Scott, Charles M. Lukehart, with portions accessible via Google Books. Table 1 shows data for many nuclei. Figure 1 shows that 35Cl NQR resonances of covalently-bonded Cl sites occur in the range of roughly 20 to 70 MHz, depending on the electronegativity of the other atom.

At first you will have to guess about the power level, pulse length, recycle delay, and number of scans. After you find a signal, you can optimize those parameters.

I have never done NQR in this way. I think this is the general approach, but I may have some details wrong.

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answered May 31 '13 at 23:53

Tony%20Bielecki's gravatar image

Tony Bielecki
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This measurement can actually be very easy to perform - provided you get a few things right.

The NQR of 35Cl in powdered NaClO3 occurs at ~29.9 MHz and gives a rather rather strong signal. The behavior of the spin system is well described in the literature (see Abragham "Principles of Nuclear Magnetism" or perform a google search on "NQR of sodium chlorate" for more information) and in some limiting cases can mimic S=1/2 behavior. However, be warned that NQR spin dynamics are, in general, very interesting and can be surprising to the uninitiated.

An intense RF field (>= 50 kHz) is helpful to keep the spin behavior simple. Actually, it is better to say that weak RF field causes additional complications. I'm uncertain about your system specs but I expect that this RF field intensity is readily available on the X channel of 10 mm liquids probes. Of course, sample spinning is, at least in the initial observations, unnecessary.

The spin behavior can be perturbed by the application of a small permanent magnet placed near the sample. I once built a small standalone, single resonance, 29.9 MHz, NQR probe with a larger solenoid wrapped around the RF sample coil and fed to the outside world through RF-bypassed feed-thru connectors and connected to DC pulsing circuitry. The NQR signal can exhibit very interesting Zeeman splitting (see above references) and interesting multi-dimensional experiments can be devised.

Large crystals of sodium chlorate can be prepared easily by slow evaporation from aqueous solution at room temperature. This kind of sample combined with multiple axis pulsed DC field coils can offer even more complicated and interesting experiments.

Back in the day (late 80s - early 90s ish) when I was working at Chemagnetics, Inc. (a manufacturer specializing in solid-state NMR spectrometers and such) we used to use NQR as part of the console qualification process before it would be mated with a magnet. We also brought these devices to conferences, like the ENC, to play with.

Lastly, I will take this opportunity to acknowledge and thank a great spectroscopist, Rodney Farley, then of the DuPont company, for introducing me to NQR spectroscopy way back then.

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answered Jun 03 '13 at 08:35

Joseph%20DiVerdi's gravatar image

Joseph DiVerdi
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From the literature find out a organic compound with the NQR nucleus having the Nitrogen 15N - 50.684.

From reference http://www.znaturforsch.com/aa/v58a/s58a0220.pdf find that the NQR frequency of 35 Cl isotope is around 29-36 Mhz and by a more specific search it must be easy to get a 35Cl compound (must be easy to procure from Stock) which has 35Cl resonance frequency around 29-30 MHZ, and some copounds with frequencies about %0 MHz also are listed. If the probe can be set for 15N at 50.684, this means the probe must be capable of getting tuned in the vicinity of 50.684 MHz.

try to procure a sample with 35Cl whose NQR frequency has been reported in the literature to be nealy 50.684 MHZ. Note the NQR resonance frequency from literature, tune the probe to exactly thsi frequency of 35Cl NQR. If you succeed, then turn off the console and shut the system down.

Remove the probe only from the magnet and you may even let the probe assembly be placed to lie on the ground (it need not be kept vertical and held vertical). Then, fill in the sample tube with the 35Cl compound and put in this sample into the probe again letting it be outside the magnet assembly. Turn on the console tune the probe precusely for the NQR frequency (around 50.684 MHz) and by a single pulse experiment it should possible to detect the NQR signal.

Aravamudhan

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answered Jun 04 '13 at 04:44

SankarampadiAravamudhan's gravatar image

SankarampadiAravamudhan
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Asked: May 26 '13 at 05:28

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Last updated: Jun 04 '13 at 04:44

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