Accession Number:

ADA248567

Title:

Measurement of Radiative Lifetimes of Vibrational States of Simple Ions

Descriptive Note:

Final rept. Sep 1987-Oct 1991,

Corporate Author:

PARIS-11 UNIV ORSAY (FRANCE) LAB DE PHYSICO-CHIMIE DES RAYONNEMENTS

Personal Author(s):

Report Date:

1991-12-31

Pagination or Media Count:

9.0

Abstract:

A unique differentially pumped triple cell FTICR machine, where production of the ions, storage in a high vacuum trap for variable relaxation times and chemical monitoring of the internal energy content of the ions are separated as well in space as in time, has been shown to be well suited for experimental determination of radiative lifetime of ions. The monitor ion technique relies on the availability of energetically appropriate ion molecule processes, usually charge or proton transfer reactions. When several levels are populated, only overall lifetimes can be experimentally determined and correction of the raw data for radiative cascade is needed to get individual lifetimes. The reliability of this technique has been demonstrated for NOX, v1-4 where accurate ab-initio calculations exist. For HCIDCIX, vl the agreement with theoretical calculation is reasonable. For polyatomic ions our method can only indicate the presence and measure the relaxation rate of the amount of energy needed to drive the monitor reaction. However this proved quite valuable in the case of the acetone ion, revealing the unexpected possibility to store a substantial amount of internal energy for milliseconds. For some triatomic and tetratomic ions like HCO, H2O NH3, our preliminary results have to be confirmed and completed with the newly improved experimental set-up. Reduction of collisional quenching in the relaxation cell by a double differential pumping will allow measurements of lifetimes up to approximately one second.

Subject Categories:

  • Atomic and Molecular Physics and Spectroscopy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE