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# Accession Number:

## AD0608708

# Title:

## SPIN-ECHO STUDIES OF CHEMICAL EXCHANGE. II. CLOSED FORMULAE FOR THE T-2 OF TWO SITES.

# Descriptive Note:

## Technical rept. no. 76,

# Corporate Author:

## ILLINOIS UNIV URBANA NOYES CHEMICAL LAB

# Report Date:

## 1964-09-29

# Pagination or Media Count:

##
49.0

# Abstract:

## Closed expressions are derived for the decay in amplitude of successive echoes in nuclear magnetic resonance experiments for systems with two exchanging sites having different resonance frequencies but equal transverse relaxation times in the absence of exchange. The decay is found to be the sum of two exponential terms and two pseudo-exponential terms the absolute values of the latter decay exponentially but the sign alternates from one echo to the next. For the case of two equally populated sites the decay simplifies to the sum of just one exponential and one pseudo-exponential term. In most cases of experimental importance a single exponential term is much larger than the rest and adequately describes the decay in echo amplitude. An iterative computer procedure is described which uses the expressions to extract information about the system from measurements of the apparent decay time constant as a function of 180 degree pulse separation. Author

# Distribution Statement:

## APPROVED FOR PUBLIC RELEASE

#