Measurement of the Spin-Lattice Relaxation Times of

NOTES

3204

2.4

bonds to these atoms are broken (the recoil energy of Patis of the order of 200 kev.) and that, subsequent to the themahation of these atoms (little ionhation is expected), the resulting species are either oxidized or reduced by their immediate surroundings to form matrix-stabikd precursors of the observed products.

I

I

2.0 nCCHJ

TI (Sec.)

1.6-

Measurement of the Spin-Lattice Relaxation Times of Dimethyloctylamine Oxide through

1.2-

the Critical Micelle Concentration I

,

by Kenneth D. Lawson and Thomas J. Flautt Ths Procter & &mbk Company, Miami VauSy Laboratories, Cin&nn&i, Ohw &%S9 (Received May S,1986)

Figure 1. Spin-lattice relaxation times of DCAO aa a function of concentration.

The nuclear spin-lattice relaxation times (TI) of the various proton moieties of the nonionic surfactant dimethyloctylamine oxide [CHa (CHZ)7N(0)(CHa)2 1 (DCAO) have been determined. The measurements were made on oxygen-free solutions of DCAO in DzO at 32”. A Varian Associates Model A-60 spectrometer was used and the TI values were determined by the progressive saturation meth0d.l A “doped” water sample with a known relaxation time was used to calibrate the instrument. The preparation of the surfactant has been described elsewhere.2 The experimental TI values are shown in Figure 1 as a function of the concentration of DCAO in moles per liter. There was no indication that there is more than one TI for a band of a given chemical shift. However, the method used to determine the relaxation times would indicate multiple T1values only if a substantial distribution were present. All of the TI values show an apparent maximum near the critical micelle concentration (c.m.c.) of the surfactant.* The magnitudes of < T ~ , N c