An electrospray apparatus for deposition of organic molecules on surfaces in ultrahigh vacuum is presented. The kinetic energy at the impact and mass to charge ratio of deposited ions can be controlled by an electrostatic quadrupole deflector and an in-line quadrupole mass spectrometer. With an ion funnel in the first two vacuum stages a high ion transmission is achieved. Experiments on porphyrin cations and deoxyribonucleic acid deposited on a Au(111) surface demonstrate the capabilities of the instrument.

A significant reduction in the Atlantic Meridional Overturning Circulation and rapid northern Hemisphere cooling 8200 years ago have been linked to the final melting of the Laurentide Ice Sheet. Although many studies associated this cold event with the drainage of Lake Agassiz-Ojibway, recent model simulations have shown that the Hudson Bay Ice Saddle collapse would have had much larger effects on the Atlantic Meridional Overturning Circulation than the lake outburst itself. Based on a combination of Mg/Ca and oxygen isotope ratios of benthic foraminifera, this study presents the first direct evidence of a major Labrador shelfwater freshening at 8.5 ka BP, which we associate with the Hudson Bay Ice Saddle collapse. The freshening is preceded by a subsurface warming of the western Labrador Sea, which we link to the strengthening of the West Greenland Current that could concurrently have accelerated the ice saddle collapse in Hudson Bay.

A Mn-porphyrin was contacted on Au(111) in a low-temperature scanning tunneling microscope (STM). Differential conductance spectra show a zero-bias resonance that is due to an underscreened Kondo effect according to many-body calculations. When the Mn center is contacted by the STM tip, the spectrum appears to invert along the voltage axis. A drastic change in the electrostatic potential of the molecule involving a small geometric relaxation is found to cause this observation.

Ruthenium dyes (N3) are deposited by in situ ultrahigh vacuum (UHV) electrospray ionization on a Au(111) surface and investigated using scanning tunneling microscopy and spectroscopy. The molecules exhibit some fragmentation at deposition energies around 7 eV, while deposition of intact molecules is feasible with energies of 2.5 eV. A variety of adsorption geometries is found that are analyzed using spectroscopy of vibronic excitations and DFT calculations. ■ INTRODUCTIONThe dye N3 (cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)-ruthenium(II), Figure 1a) is one of the most efficient sensitizers in dye-sensitized solar cells (DSCs), which are an appealing alternative to Si-based solar cells. 1,2 The conversion efficiency of DSCs depends on the intramolecular metal-to-ligand charge transfer as well as the charge transfer to and from the electrode materials (Au(111) 3 and TiO 2 4 ), which in turn are affected by the adsorption geometry of N3. On TiO 2 surfaces, N3 adsorbs via two deprotonated carboxylic groups and one isothiocyanate. 5−8 As to adsorption on Au(111), previous photoelectron spectroscopy (PES) data has been interpreted in terms of S atoms of the N3 bonding to Au. 9 Due to N3 being a rather fragile molecule, the possibility of fragmentation should be considered. Compared to a spatially averaging method, microscopic techniques like scanning tunneling microscopy (STM) may be advantageous to detect and possibly identify fragments or conformers of adsorbed N3. The deposition of N3 on surfaces in ultrahigh vacuum (UHV) is indeed challenging because the molecule is not stable enough for thermal sublimation. Electrospray ionization (ESI) is an attractive alternative for transferring fragile molecules into the gas phase for UHV investigations. 7,10,11 Mass filtering of the ions may be used to ensure that only intact molecules arrive at the substrate.To avoid fragmentation during the adsorption process (softlanding), it is crucial to control the kinetic energy of the ions. 12−21 When metal clusters are deposited, soft-landing may be achieved at kinetic energies ranging from 0.1 to 1 eV per cluster atom. 16,22 Estimates for the deposition of complex molecules are usually less favorable owing to the varying characteristics of the molecular bonds. 15,16,23−27 For enzymes, a soft-landing energy of only ∼3 eV per charge has been reported. 25 On the other hand, in a recent work utilizing scanning photoluminescence spectroscopy and time-of-flight secondary mass spectroscopy, rhodamine 6G was reported to withstand deposition energies that are comparable with the upper limit for metal clusters (1 eV per cluster atom). 16 The fraction of the collision energy which is transferred to internal degrees of freedom of the molecule and therefore available for fragmentation can be obtained from surface-induced collision (SID) studies ∼10−30%. 28−30 Here we investigate ultrahigh vacuum ESI deposition of N3 on a Au(111) surface. We find partial fragmentation of N3 on the Au(111) surface at a deposition energy of...

Radiocarbon (14C) results on cremated bone are frequently published in high-ranking journals, but 14C laboratories employ different pretreatment methods as they have divergent perceptions of what sources of contaminants might be present. We found pretreatment protocols to vary significantly between three laboratories (Brussels [RICH], Kiel [KIA], and Groningen [CIO]), which all have a long history of dating cremated bone. We present a case study of 6 sets of replicate dates, to compare laboratory pretreatment protocols, and a further 16 sets of inter-laboratory replicate measurements, which compare specific steps of the conversion and measuring process. The 14C results showed dates to be reproducible between the laboratories and consistent with the expected archaeological chronology. We found that differences in pretreatment, conversion to CO2 and accelerator mass spectrometry (AMS) measurement to have no measurable influence on the majority of obtained results, suggesting that any possible diagenesis was probably restricted to the most soluble ≤5% of each sample, as this proportion of the sample mass was removed under all laboratory protocols.