Measurement of short lifetimes in highly-charged ions using a two-foil target

Technical Report · Tue Aug 01 04:00:00 EDT 1995

DOI:https://doi.org/10.2172/166490· OSTI ID:166490

Berry, H. G.; Dunford, R. W.; Gemmell, D. S. ^[1]

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1. and others

One of the frontiers in the study of the atomic physics of highly-charged ions is the measurement of lifetimes in the 100 fs to 10 ps regime. The standard technique for measuring lifetimes of states in highly-charged ions is the beam-foil time-of-flight method in which the intensity of an emission line is monitored as a function of the separation between the exciting foil and the portion of the beam being viewed by the detector. This method becomes increasingly difficult as the decay lengths of the states of interest become shorter. At a typical beam velocity of 10% of the speed of light, the beam travels 30 microns in a picosecond. The standard beam-foil time-of-flight method necessitates observation of the decay radiation within one or two decay lengths from the foil while preventing the detectors from observing the beam spot at the foil. For short-lived states this requires tight collimation of the detector with a resulting loss in solid angle. We are developing a method for measuring ultrashort atomic lifetimes utilizing a two-foil target. As a specific case to demonstrate the feasibility of our method, we are studying the decay of the 2 {sup 3}P{sub 2} level in helium-like Kr{sup 34+}. This level has a calculated lifetime of 9.5 ps which corresponds to a decay length of 380 {mu}m. For krypton, theory predicts that 90% of the 2 {sup 3}P{sub 2} states decay via M2 radiation to the ground state. A measurement of the lifetime of this state would contribute to an important current problem which concerns the understanding of atomic structure when both electron correlations and relativistic effects are simultaneously important.

• Research Organization: Argonne National Lab., IL (United States)
• OSTI ID: 166490
• Report Number(s): ANL--95/14; ON: DE96000985
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ENERGY-LEVEL TRANSITIONS
KRYPTON IONS
LIFETIME
MEASURING METHODS
MULTICHARGED IONS
PROGRESS REPORT
TIME-OF-FLIGHT METHOD