No abstract

The spectra emitted in the decay of the first excited states of the (RgA)+ ions with Rg = Ar, Kr or Xe and A = Li, Na, K, Rb or Cs have been investigated. The emission of these excimer-like ions is in the vacuum ultraviolet region and hence they are of interest for possible lasers operating in the vuv. Each ion decays by emission of 3 or 4 continua.Based on recent ab initio calculations by Markert er a1 the transitions are assigned to the decay of the 0 = 1 and O+ levels of the (RgA)+ ions correlating with the asymptotic states Rg+(2P3,2)+A. In the (ArA)+ ions the doublet expected for the (RgA)+ ions with a Rg+(*P,,*) + A asymptotic state was also observed.

No data are available on surface currents of the central or northern Great Barrier Reef lagoon. Here we describe the fine-scale surface currents for Cid Harbour, Whitsunday Island group, Queensland, Australia, from 170 drogue releases and extensive aerial photographs. The current regimen is dominated by the strong tidal race to the south through the Whitsunday Passage toward Broad Sound, which experiences an 8-m fall during spring tides. Although the tidal cycle in Whitsunday Passage is symmetrically semi-diurnal, currents in adjacent Cid Harbour are asymmetric, with approximately 8-h southerly floods and 4-h northerly ebbs. This asymmetry is caused by topographic peculiarities of the Whitsunday Archipelago. Headlands and embayments within the harbour generate sharp shear zones, gyres, eddy systems, edge effects, convergences and divergences, and these dominate the fine-scale surface current patterns. In turn these local surface phenomena, particularly shear zones, affect the microdistribution of zooplankton. The flood tide in Cid Harbour is responsible for the depositional pattern of sediments and controls the morphology of coral islands within the habour. Cid Harbour is in the lee of Whitsunday Island and wind does not greatly affect surface currents. The importance of fine-scale current patterns has been underestimated, particularly by planktologists and reef morphologists.

Ionic rare gas alkali excimers Rg+A were produced by exciting Rg/A mixtures in a buffer gas atmosphere by means of an ion or electron beam. As a representative candidate the formation of Kr+K decaying at 135 nm was investigated. The rate constant k(He) for the main reaction Kr++K→Kr+K was determined varying the buffer gas density [He] between 1017 and 1020 cm−3. Values between k(He)=1×10−11 and 5×10−10 cm3 s−1 were observed. At high buffer gas densities the quantum yield ηq for the emission of the 135 nm radiation depends on the ratio [K]/[Kr]. At the optimum value, [K]/[Kr]=0.06, an absolute yield of ηq=1.5% was obtained. Up to a deposited energy of 3 mJ/cm3 the quantum yield is independent on the excitation density. For neon as buffer gas the rate constants k(Ne) are smaller by about a factor of 3, while the efficiency is only slightly less than for He. Kr+K is split into five fine structure states. The quenching of these states by krypton and buffer gas causes the low quantum yield.

Ionic excimers, which are isoelectronic to the rare gas halides, are investigated. In a charge transfer reaction of He+ or Ne+ ions to CsF and RbF, continua in the VUV at 184.5 and 131 nm, respectively, have been observed, which show the same properties as the analogous transitions in the rare gas fluorides. The results are compared with predictions by a Rittner model. In KF a transition at 143 nm was observed which could be assigned to the transition of KF+→K+F.