A resonance ionization time of flight mass spectrometer with a cryogenic sample concentrator for isotopic analysis of krypton from extraterrestrial samples

摘要: RIMSKI – Resonance Ionization Mass Spectrometer for Krypton Isotopes is a newly developed ultra sensitive instrument with cryogenic sample concentrator and laser ion source designed isotopic analysis of extraterrestrial material. Laser heating used extraction krypton from samples into the mass spectrometer volume. Atoms continuously condense on cold spot in source, are repeatedly released by heating. They ionized evaporation plume using three tunable dye lasers one frequency tripled Q-switched Nd:YAG laser. Two resonant transitions employed (at 116.5 nm, produced four-wave mixing Xe, 558.1 nm) followed single photon ionization at 1064 nm. Multiple analyses air aliquots <5 mg meteorites, both containing ∼106 total atoms, show precision ∼1% major isotope ratios. reproducible to this level through day's analyses, allowing calibration linear non-linear discrimination sample-standard bracketing. Cosmogenic 81Kr can be reliably detected few thousand atom level, corresponding determination cosmic ray exposure (CRE) ages meteorite milligrams. Measured CRE noncumulate eucrites are: Pasamonte, 7.9 ± 1.3 My; Sioux County, 20.9 4.0 Bereba, 23.7 2.6 Stannern, 33.3 2.5 My. These good agreement literature values.