LASER SPECTROSCOPIC STUDIES OF BOUND AND AUTOIONIZING SERIES OF YTTERBIUM

RAHEEL, ALI (1999) LASER SPECTROSCOPIC STUDIES OF BOUND AND AUTOIONIZING SERIES OF YTTERBIUM. Doctoral thesis, Quaid-i-Azam University, Islamabad.

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Abstract

The present work is devoted to study the bound and autoionizing Rydberg states of ytterbium employing the multistep and multiphoton laser excitation schemes in conjunction with a thermionic diode ion detector. Different intermediate levels have been used, 6s5dI D2, 6s6p 3pI, 6s7s3 SI and 4f13 (2F7/2)6s2 6d[3/2]I to record the spectra of ytterbium. The 6s5dI D2 intermediate level was populated via a two-photon excitation and the second laser was scanned to observe the l = 1 and 3 Rydberg levels. The 6s6p3 PI intermediate level was populated via single photon excitation and from this level the upper levels were excited via two-photon absorption. As a result, in the bound region, the 6snf 1,3 F3 (9≤ n ≤ 30), 6snpI pI (12 ≤ n ≤ S6), 6snp 3PI (12 ≤ n ≤ SO) and 6snp2 P2 (12 ≤ n ≤ 42) Rydberg series have been observed. Three new levels due to the 4f-innershell excitation 4p13 5d2 6s3 D3, 4f13 5d2 6sI F3 and 4f13 5d2 6s3 G3 , which serve as perturbers have been identified. In order to describe the interchannel interactions among the J = 2 and J = 3 channels, the multichannel quantum defect theory have been used which supplements the level assignments. To approach the levels lying above the first ionization threshold, the 4f13( 2F7/2)6s2 6d[3/2]1 intennediate level was populated via the 6s7s3 S1 level (two-photon excitation) while the third laser was scanned. The first measurements of the even parity autoionizing resonances due to the 4f-innershell excitation are reported using three-color four-photon resonant excitation technique. The 4f13(F7/2)6s2 np[5/2]2 (12 ≤ n ≤ 4S) and 4f13 (2F7/2)6s2 nf [5/2]2 (9 ≤ n ≤ 33) have been observed. The spectral line shapes and their intensities have also been discussed.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: laser spectroscopic studies, ytterbium,laser excitation schemes, photon resonant excitation, thermionic diode detector
Subjects: Q Science > QC Physics
Depositing User: Muhammad Khan Khan
Date Deposited: 26 Sep 2016 10:18
Last Modified: 26 Sep 2016 10:18
URI: http://eprints.hec.gov.pk/id/eprint/1613

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