CLICK HERE to view the Letter of Invitation to CMDAYS04 Symposium
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Sec.5. Java Features:Excerpts from previous presentations & Reports |
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http://nehuacin.tripod.com/id3.html
The Link on the left displays a page of the poster site at the this is a SSNMR event organised by the Groupment Ampere subsequent to 17thEENC/32nd Ampere at Lille, France in Sept. 2004 This author did not attend the EUROMAR2005 at Veldhoven, The Netherlands |
| CLICK HERE to display the WebPage for this author's participations during Winter 2005-2006 |
| Dr.S.Aravamudhan CLICK HERE |
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From:Ampere-EENC-2004 Conference
To: amudhan2000@rediffmail.com
Subject: Presentation of the EENC/AMPERE 2004 Conference.
Date: Wed, 14 Apr 2004 15:41:23 IST
17th EENC / 32nd AMPERE - Lille (FRANCE), September 2004
The joint conference will be held in Lille (FRANCE)
from 6th to 11th September 2004.
Devoted to all aspects of magnetic resonance,
the conference will gather numerous scientists
All available information about this event is
on the website: http://www.nmr2004.com
CLICK on the photograph on the right to dispaly an index page---->>
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LINESHAPES IN SOLID STATE NMR Sankarampadi ARAVAMUDHAN Department of Chemistry North Eastern Hill University Shillong (Meghalaya) 793022 INDIA E Mail: saravamudhan@nehu.ac.in It has been pointed out earlier that a simple programmable summation procedure can be used to calculate the demagnetization factors which otherwise require evaluation of elliptic integrals [1]. This summation procedure was a result of the extended consideration of the calculation of intermolecular shielding contributions for extracting the isolated molecule value for the proton shielding parameters from a measurement by the HR PMR techniques . The effort to find possibilities to reduce the stringency[2]of the requirement of a spherical sample for such measurement leads to the necessity to consider such a summation within the Lorentz ellipsoids [3]. These results now stand to be reconciled with the susceptibility effect measurements in liquid state HR PMR experiments[4]. This summation procedure seems to be valid for applying point dipole approximations, even for a macroscopic sample, to calculate the induced field outside and near the magnetized specimen[5]. The induced fields in and around the specimen using this method in solids and the comparison with liquids would be discussed. |
CLICK HERE to display a WebPage from where the POSTER Presentation Sheets can be viewed
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Dr.S.Aravamudhan CLICK HERE |
In the Submitted Abstract
Multiple-NMR-Experimente an Molekulkristallen und ab-initio Rechnungen"
Inaugural-Dissertation zur Erlangung der Doktorwurde
der
Ruprecht-Karls-Universitat Heidelberg
Vorgelegt von Dipl.-Phys. Bernd Tesche
Prufung 19-07-1995
Gutachter: Prof.Dr. Ulrich Haeberlen
Page 24 Page 25 Page 26 Page 27
The TEXT of the notes appear after the text of the message.
Dear Sankarampadi or dear Aram, as we used to call you,
it was a real joy to receive mail from you and to learn that you are
still travelling to conferences and that you are still pondering on
questions initiated a long time ago in Heidelberg.
Actually, I have to think myself on such matters:
I am preparing a manuscript dealing with the question what the relations
are in the benzene molecule between the principal
shielding components and principal directions, fixed by molecular
symmetry. The eventual answer is this:
least shielded direction - perpend. to molec. plane; most shielded direction:
- in-plane-perpendicular-to-the-bond. Has that been known [1] to you?
The experiments were done on biphenyl, with particular
attention to the H-atom in para-position. Of course, the analysis of the
data requires knowledge of the intermolecular [2] shielding contributions.
Our approaches: point dipole calculation as in 1979 and ab-initio calculations for clusters.
If you are aware of any work [3] on proton shielding tensors (either expl.or theor., after 1995)
of aromatic systems, I would be very grateful to learn about it.
A few comments on your posters:
(1) So long as you shift all your small dipoles (length l) to the
midpoint of the large dipole (L), I would expect the result to be the same. [4]
Things will be different if the small dipoles are shifted to a variety (a distribution)
of different places.
(2) Ellipsoid: the more interesting situation is to have the
proton site and the small blue ellipsoid off-center from the large one.. [5]
(3) Be aware that nobody tries any more to measure proton shift
tensors via line narrowing multiple pulse sequences. In fact,nobody anymore has
the necessary equipment. If I am wrong, please let me know.
(4) Did you have a look at Prigl`s article in Adv.Magn.Reson.,Vol.19, 1996?
He actually used an ellipsoidal sample. Also, did you see
our 2001 deuteron NMR paper in JMR on Ca-formate? We claim it contains the most
accurate measurement of the shielding tensor of an H atom.
Best regards Ulrich Haeberlen
***************************
Dr.S.Aravamudhan,M.Sc.,Ph.D
Lecturer,North Eastern Hill University,Mawkynrow,Umshing,Shillong 793022
East Khasi Hills District
Meghalaya INDIA
Tel: 91 364 2550041/2722464
Fax: 91 364 2550486/2550076
EMail: amudhan2000@rediffmail.com
amudhan20012000@yahoo.co.in
saravamudhan@nehu.ac.in
***************************
NOTES
[1]. "Pyromellitic acid dianhydride: crystal structure and anisotropic proton magnetic shielding" S.Aravamudhan et.al Molecular Physics,1979, Vol.38,No:1,241-255.
particular page 249 (in the 2nd paragraph):....." In the case of protons attached to an aromatic ring, it is reasonable to expect the normal of the molecular plane to be the least shielded direction due to the deshielding effect of the ring current."
and(in the 4th paragraph):....."it should be borne in mind that as long as we cannot predict the direction and size of the intermolecular contributions, there is no a priori reason to expect that the relation between the least shielded direction and the normal to the molecular plane should remain unaltered by the intermolecular contributions."
[2]. " Intermolecular Contributions to the Chemical Shielding Anisotropy in Crystalline Benzene" T.Barbara, C.F.Wood, and B.P.Dailey., Journal of Magnetic Resonance, 1982, Vol.48., 225-233.
particular page 232 (in the 2nd paragraph):...."A recent study of single crystal of pyromellitic acid dianhydride also shows increases in the asymmetry parameter and decreases in the anisotropy resulting from intermolecular effects (S.Aravamudhan et.al., Mol.Phys.,1979,Vol. 38, p241). The pyromellitic acid study is particularly interesting in that there is no molecular rotation, so that acomplete single crystal study yields the asymmetry parameter"........".The corrected tensor yields anisotropy =-5.43 ppm and asymmetry =0.6. An estimated contribution of 2 ppm from the carbonyl groups to the deshielding perpendicular to the aromatic plane can be used to give anisotropy =-3.44 ppm for an aromatic proton."
[3]. ." Investigating the Feasibility of the Use of magnetic Dipole Model for Intramolecular Proton Shileding in Benzene." S.Aravamudhan,Joint ISMAR-CA '98 TU Berlin Aug.1998 URL: http://saravamudhan.tripod.com/id2.html and the URL: http://www.geocities.com/amudhan20012000/ismar_ca98.html (at this URL also find page naviagtion to a CRSI event at IIT/Madras, July 12-13,2006.
[4]. About this point a POSTER presentation was made in one of the National Symposia in Chemistry.This material is documented at the webpage built by this author exclusively for this purpose. Particularly the display SHEET-10 (CLICK here to download )contains the main argument for this point.In the reference cited for NOTE:[1] above, on page 252, below the equation-(3) the criticality of the point dipole approximation in certain contexts is discussed at length in the third paragraph of the page.
[5]. The power point file which was used for the presentation at the recently {7-20. February 2004}held National Symposium [NMRS2004]of the National Magnetic Resonance Society at Kolkata contains the main result similar to the point raised here. It is only required to add that,in the case of ellipsoid which is a weel established case of homogeneous magnetization for a uniform susceptibility of the specimen, placing the inner ellipsoid would only prove that the calculational procedure is valid if at all points within the same specimen the demagnetization factor value is the same. The presentation at NMRS2004 is on specimen shapes where in the magnetization is not homgeneous even for uniform susceptibility through out the specimen.
CLICK HERE for an Abstract entitled..: "SHAPE DEPENDENT FIELD INHOMOGENEITY OF HOMOGENEOUS SPECIMEN: CONSEQUENCES IN HR PMR IN SOLIDS"
SECTION-5
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find in Sec.2. above the TEXT of ABSTRACT submitted for consideration at the Joint 17thEENC/32ndAmpere in France/Lille,Sept.2004 Dr.S.Aravamudhan CLICK HERE  Click to join user_magnetic_resonance |
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