Date of Award


Degree Type


Degree Name

Doctor of Philosophy


A new high-efficiency photon-photon delayed coincidence lifetime measuring apparatus has been constructed and was used to study the 5d {dollar}\sp4{dollar}F{dollar}\sb{lcub}9/2{rcub}{dollar} {dollar}\longrightarrow{dollar} 5p {dollar}\sp4{dollar}D{dollar}\sbsp{lcub}7/2{rcub}{lcub}\rm o{rcub}{dollar} {dollar}\longrightarrow{dollar} 5s {dollar}\sp4{dollar}P{dollar}\sb{lcub}5/2{rcub}{dollar} cascade in Kr II and the 6d {dollar}\sp4{dollar}F{dollar}\sb{lcub}7/2{rcub}{dollar} {dollar}\longrightarrow{dollar} 6p {dollar}\sp4{dollar}D{dollar}\sbsp{lcub}5/2{rcub}{lcub}\rm o{rcub}{dollar} {dollar}\longrightarrow{dollar} 6s {dollar}\sp4{dollar}P{dollar}\sb{lcub}3/2{rcub}{dollar} cascade in Xe II. A neutral atomic beam was excited and ionized by electron impact, and the spontaneously emitted photons were collected by an ellipsoidal mirror, collimated by an aspheric lens, and detected by two Amperex XP2020Q fast linear-focussed photomultipliers provided with narrow-band interference filters. The spectrum of time delays was acquired by a time-to-amplitude converter-multichannel pulse-height analyser combination. The lifetime of the Kr II 5p {dollar}\sp4{dollar}D{dollar}\sbsp{lcub}7/2{rcub}{lcub}\rm o{rcub}{dollar} state was found to be 7.004 {dollar}\pm{dollar} 0.053 nanoseconds and is in agreement with two previous measurements. This first measurement provided a calibration of the newly constructed apparatus. It also has provided an improvement in the precision with which this lifetime is known by a factor of 3. The Xe II 6p {dollar}\sp4{dollar}D{dollar}\sbsp{lcub}5/2{rcub}{lcub}\rm o{rcub}{dollar} state lifetime was found to be 9.634 {dollar}\pm{dollar} 0.067 nanoseconds. This result agrees with several measurements of lower accuracy but does not agree with two previous measurements claiming high precision. This discrepancy has not been resolved in this work.



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