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When the dipole-dipole energy transfer, Rb 25s 1/2 ϩRb 33s 1/2 →Rb 24p 1/2 ϩRb 34p 3/2 , resonant at fields of 3.0 and 3.4 V/cm, is observed in a cold Rydberg gas, the resonances are broader than expected for this dipole-dipole interaction alone. Using a variant of the Ramsey interference method, in which the system is detuned from the resonance, we observe a density-dependent dephasing which we attribute to the inhomogeneities in the always resonant dipole-dipole excitation exchange interactions Rb 25s 1/2 ϩRb 24p 1/2 →Rb 24p 1/2 ϩRb 25s 1/2 and Rb 33s 1/2 ϩRb 34p 3/2 →Rb 34p 3/2 ϩRb 33s 1/2. Since the dephasing rate is comparable to the observed widths, it appears that all of these interactions contribute to the observed linewidths.

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The laser excited fluorescence spectrum of NCO from an atmospheric pressure CH4/N2O/N2 flame is reinvestigated with a more sensitive apparatus than used previously. The NCO is pumped from the X 2Π (1,01,0) level to the A 2Σ+ (0, 00, 0) level. Emissions to (0, 01, 0)2Π, (1, 01, 0)2Π, (0, 01, 1)2Π, and (0, 10, 0)2Σ+ in the X state are observed. The previous tentative assignment of pumping transition as Q231 is confirmed. The confirmation of pumping transition solidifies our earlier interpretation that excited state spin relaxation in the flame is much faster than electronic quenching. In addition, analysis of the fluorescence spectra yields the first reported constants for the X(1, 01, 0)2Π level and spin splitting for X(0, 01, 1)2Π level in the gas phase.

SIR: Nuclear magnetic resonance (NhIR) spectrometry is very useful in elucidation of structure of amines. A proton on a nitrogen atom may undergo rapid, intermediate, or slow exchange. If the exchange is rapid, the N H proton(s) is decoupled from the N atom and from protons on adjacent carbon atoms. The K H peak is therefore a sharp singlet, and the adjacent C H protons are not split by XH. Such is the case for most aliphatic amines. At an intermediate rate of