Narrow positron peaks are observed in five supercritical collision systems with combined nuclear charge 180^ Z u ^ 188. The peaks do not originate from nuclear internal pair conversion and their production appears to occur in a narrow projectile-energy interval near the Coulomb barrier. The line shapes are consistent with emission by a source moving with the cm. velocity. Particularly notable is an apparent independence of the peak energies on Z w . These observations are discussed in the context of the spontaneous decay of the QED vacuum and other new potential sources of line positron spectra.

favored over the one observed. The calculation predicts that the |2 + -5r,-£) state will decay only to the j2 + f,|-} state. Since the 1686 state has this decay pattern and the energy predicted by the calculation, it is identified as the |2 +^, -|.) state.The shape of the calculated curves in Fig. 2 is governed by the effect of the Coriolis interaction, which reduces the energy of the states in proportion to the alignment of the total angular momentum, /, and the particle angular momentum, j. 9 I and J are aligned when R and j are aligned, or antialigned. An arch curve is expected when the Fermi surface is near the low-lying states of given parentage. A flatter curve is expected when the Fermi surface is near the higher states of a given parentage, as less alignment is possible. These are the same conditions which produce AI = 2 or A7 = 1 yrast bands. In "Ru the Fermi surface satisfies the former condition for the g 7 / 2 and h n / 2 multiplets and the latter condition for the d 5 / 2 multiplet as shown in Fig. 2.In addition to the R ^2 multiplets, states from the 4 + and second 2 + multiplets are expected. States having the energies and transition properties calculated for R ^4 multiplets have been observed. Unfortunately, the spins of many states at higher excitation energies could not be determined in the present work because of poor statistics. Thus, no reliable measure of completeness for R ^4 multiplets has been attempted. Other states are observed which do not fit into the pattern of the particle-rotor model. Thus the reaction may be more complete than has been PACS numbers: 33.20.Ea Vibration-rotation spectroscopy of charged molecules has become experimentally realizable only within the last decade, principally through the pioneering efforts of Wing and co-workers 1 and Oka 2 . Wing and co-workers have observed demonstrated for the R ^2 multiplets.As evidenced by the presented results, the ( 3 He, 2ny) reaction is a powerful tool for populating nonyrast states in a wide range of angular momenta. In fact, three complete particle-core multiplets have been observed experimentally and successfully interpreted with a particle-rotor model. The empirical results are actually more complete than the model. This completeness allows a more rigorous test of various models than has previously been possible. . vibrational spectra of HD + , HeH + , and D 3 + in fast ion beams by monitoring the changes in charge-transfer cross sections that result when vibration-rotation transitions of these ions are velocity tuned into coincidence with a CO laser.The first observation of vibration-rotation transitions in HCO + is reported. The v x absorption band was measured with a color-center laser by modulating the drift velocity of the ion in an ac discharge and detecting the Doppler-shifted absorptions with lock-in techniques.The v x frequency is determined as 3088.727± 0.003 cm" 1 .

The first high-re solution measurement of the v 3 vibration (doubly degenerate asymmetric stretch) of the hydronium ion (H 3 0 + ) is reported. An analysis of sixty transitions in the symmetric and antisymmetric inversion states yields effective band origins of 3530.165(55) and 3513.840(47) cm" 1 , respectively.