Ohio Advanced EPR Laboratory at Miami University

A resource serving the pulsed and CW EPR needs of the greater Ohio area.

 Relaxation Determination

There are two simple experiments that can be used to give a good indication of T1 and T2, which are the Inversion Recovery experiment and a 2P ESEEM measurement.

Determination of T1

The most simple experiment used to probe for T1 relation, or longitudinal relaxation due to return to thermal equilibrium is the Inversion Recovery experiment.

INVREC

Inversion Recovery of a Coal Standard Sample

Inversion Recovery of a Coal Standard Sample

In this experiment, a Hahn Echo sequence is incremented in time following an initial π pulse.  The echo first appears inverted, then crosses through zero and eventually returns to a fully positive echo.  The curve created by measuring the echo amplitude can be mathematically fit to determine the T1 relaxation time.  Show in the figure are five locations along the inversion recovery experiment.  Below you will find vector diagram simulations for the pulse sequence at that point.

 

 

Determination of T2

In addition to the nuclear modulation that is observed in a 2P ESEEM experiment, the overall decay of the echo is a function of the T2 relaxation for the system.

2PESEEM

To determine T2, the spacing between the π/2 and π pulses is varied giving a decay curve like the data set displayed below.

T2 Data

The following simulations give and approximate account of the pulse sequence and corresponding vector diagram picture at the various points in the figure.

 

 

Miami University

Department of Chemistry and Biochemistry

Ohio Advanced EPR Laboratory
701 East High Street
101 Hughes Laboratories
Oxford, OH 45056

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