Methodology and Applications of the Determination of Cosmogenic Radionuclides ¹⁰Be and ²⁶Al by Accelerator Mass Spectrometry

Abstract

The measurement of cosmogenic radionuclides 10Be and 26Al by accelerator mass spectrometry (AMS) has become an invaluable tool for dating events and processes in Quaternary geochronology, and in archaeology and paleoanthropology. Here we present an overview of the current state of research by providing the theoretical and methodological background and describe processes of sample preparation and measurement by AMS. We also summarize the main geochronology calculation models for exposure and burial dating for the above applications and analysis of extra-terrestrial materials.

Cyano-capped molecules: versatile organic materials

“…The cyano (CN) group bearing both C and N atoms in sp-hybridization is a popular substituent considered a powerful electron-withdrawing moiety with high substituent constants (Hammett σ p = 0.66; Pytela σ i = 0.525). 1 The cyano group possesses negative inductive and mesomeric effects, and the CN bond is highly polarized, which is sensitively reflected by its characteristic stretching vibration in the infrared spectra (∼2200 cm −1 ). Hence, the CN group is tremendously used as a linearly-arranged electron acceptor capable of (i) polarizing π-conjugated systems, (ii) imparting intramolecular charge-transfer (ICT) when interconnected to an electron donor, (iii) creating an electron rich part of the molecule (due to −I/M effects), (iv) reducing the LUMO level without altering the HOMO, (v) narrowing the HOMO–LUMO gap, (vi) red-shifting the longest-wavelength absorption maxima, (vii) providing a coordination site for cations and electrophiles ( via nitrogen's lone pair), while (viii) the carbon is prone to a nucleophilic attack.…”