Dear
Several of you were not on my original email list. If this is the first email you have received from me please be sure to go to the course website and download and print all pertinent material (including the earlier emails sent to the class):
http://www.nmr.ucdavis.edu/BCM230_Fall2007/bcm230.html
NOTES ON THE LECTURE:
1) The lecture material presented last Friday is the cornerstone for the rest of the course. If you have ANY problems with the material, please see me THIS week! My regular office hours are Th 3-4 PM and I am also available at other times by appointment. If you are having difficulty please let me help. My office is in the modular building in parking lot 52:
http://www.nmr.ucdavis.edu/map_to_NMR.pdf
2) The animations we viewed last Friday are available for
viewing on the
http://www.nmr.ucdavis.edu/BCM230_Fall2007/Animations.html
3) It is important to remember that the carrier and Larmor frequencies are both on the order of Megahertz but their difference (which is the frequency of the FID) is on the order of kilohertz. Kilohertz frequencies are in the audible range and people in the lab Friday were able to listen to a FID the way we listened to the guitar in lecture.
4) Here is a summary of the information present in a FID:
a. The frequency of oscillation of the FID determines the frequency difference of the peak from the carrier (hence determining chemical shift relative to the carrier).
b. The INITIAL amplitude of the FID determines the amplitude of the peak in the spectrum.
c. The rate of decay of the FID determines the linewidth of the peak (we will look more at this in the next lecture).
BOTTOM
5) More explanation on quadrature phase detection (QPD): If two peaks are equally spaced +-5 kHz from the carrier their frequency of oscillation in the FIDs will be equal. There is no way to distinguish between them except by QPD. Look again at the figure on the bottom of p.21. The behavior of the +-5 kHz Larmor frequencies are identical when viewed only along the Y'-axis. However data collected on the X'-axis shows a 90 degree phase shift (frequency & amplitude are still equal!) and this phase difference allows the spectrometer to assign one Larmor frequency as + relative to the carrier and one as -. (And the total separation between the two peaks would be 10 kHz).
6) A question in lab concerned "where" to place
the carrier frequency. On a modern NMR spectrometer the software easily allows
one to place the carrier at any point in the spectrum. The carrier is generally
placed in the center of the spectrum and the sweepwidth
reduced to a minimum value that encompasses the peaks of interest. Note that
the placement of the carrier has nothing to do with chemical shift of a peak in
ppm from the
7) Note that the FID oscillation frequency will increase as peaks get farther from the carrier on BOTH the + and - frequency sides of the carrier! (But QPD will still be able to distinguish the sign + or -).
8) Next Friday we will cover pages 28 to 39 of the Notes, please read this material before the next lecture. Please also read over the short section on p.2-3 of the Appendix that covers Probe Tuning.
FOR THOSE IN THE LAB:
This Friday everyone in the lab sections will need to pay
for the course. I believe almost all of you will be able to recharge this to
one of your research advisor's UCD accounts, i.e. the four or seven digit code
you ordinarily use to purchase supplies, etc. on campus. Some can also apply
their research advisor’s NMR Award to the cost of the lab. A few of you may not
have research advisors or lack funding; in that case you will need to make out
a check for $330 to the Regents of the