The equation I=A1*EXP(-T/TAU)+A3 is generally used for calculation
of spin-lattice relaxation times. It was introduced by Sass and
Ziessow J.Magn.Reson. 25,263(1977). This paper also explains how the
parameters are calculated.
Latter Ejchart et all. J.Magn.Reson. 59,446(1986) proved that using
this equation for T1 calculation could give wrong results, and
proposed a correct method. For some reason both Bruker and Varian
still use the older algorithm.
Krzysztof Wroblewski
>>Date: Thu, 19 Apr 2007 12:54:38 -0500
>>From: Shawn Carter <scarter_at_ou.edu>
>>Subject:
>>To: susan Alguindigue <SusanA_at_chemdept.chem.ou.edu>
>>X-Mailer: Apple Mail (2.752.3)
>>X-IronPort-AV: i="4.14,428,1170655200"; d="scan'208,217";
>> a="288019031:sNHT13143836146"
>>Original-recipient: rfc822;SusanA_at_ou.edu
>>
>>Susan:
>>
>>We were hoping you could post the following question on one of the
>>NMR boards for us.
>>
>>We are performing a series of kinetics experiments with the NMR
>>that involve increasing exponential signals. According to page 138
>>of the VnmrJ Liquids NMR User Guide we can use the software to
>>evaluate the data for us. According to the guide, the software
>>uses the following equation:
>>
>>
>>I=A1*EXP(-T/TAU)+A3
>>
>>Are questions are:
>>
>>What are A1 and A3?
>>
>>How does the software find TAU?
>>If we analyze 119 spectrum of an array experiment, we seem to be
>>getting surprisingly different answers (using the kinetics program
>>built into the Varian software) than if we do a full analysis of
>>120 spectrum. Seemingly, to us, there is not much difference in
>>the 120th spectrum. At least not enough to change our answer.
>>
>>We appreciate the help,
>>
>>Shawn
>>************************************************
>>Shawn M. Carter, Ph.D.
>>Dept. of Chemistry and Biochemistry
>>University of Oklahoma
>>620 Parrington Oval
>>Norman, OK 73019
>> Tel: 405-325-2378
>>Fax: 405-325-6111
>>email: <mailto:scarter_at_ou.edu>scarter_at_ou.edu
>>************************************************
>>
>Susan L. Nimmo, PhD
>NMR Facility Manager
>Department of Chemistry and Biochemistry
>University of Oklahoma
>620 Parrington Oval, Room 208
>Norman, OK 73019
>
>Office (voice): (405) 325-0677
>FAX: (405) 325-6111
>LAB: (405) 325-2843
>CELL:(405) 627-7044
--
Krzysztof P. Wroblewski, Ph.D.
University of Pennsylvania School of Medicine
Room 96 John Morgan Building
Philadelphia, PA 19104-6055
phone: (215) 898-6396 fax: (215) 898-5642
Received on Mon Apr 23 2007 - 11:22:15 MST