Collier, Martin A. and McCaffrey, John G.
Luminescence spectroscopy of matrix-isolated z 6P state atomic manganese.
Journal of Chemical Physics, 122.
The relaxation of electronically excited atomic manganese isolated in solid rare gas matrices is observed from recorded emission spectra, to be strongly site specific. z 6P state excitation of Mn atoms isolated in the red absorption site in Ar and Kr produces narrow a 4D and a 6D state emissions while blue-site excitation produces z 6P state fluorescence and broadened a 4D and a 6D emissions.
Mn/Xe exhibits only a single thermally stable site whose emission at 620 nm is similar to the broad a 6D bands produced with blue-site excitation in Ar and Kr. Thus in ArsKrd, excitation of the red site at 393 s400d nm produces narrow line emissions at 427.5 s427.8d and 590 s585.7d nm. From their spectral positions, linewidths, and long decay times, these emission bands are assigned to the a 4D7/2 and a 6D9/2 states, respectively. Excitation of the blue site at 380 s385.5d nm produces broad emission at 413 s416d nm which, because of its nanosecond radiative lifetime, is assigned to resonance z 6P!a 6S fluorescence. Emission bands at 438 s440d and 625 s626.8d nm, also produced with blue-site excitation, are broader than their red-site equivalents at 427.5 and 590 nm s427.8 and 585.7 nm in Krd but from their millisecond and microsecond decay times are assigned to the a 4D and a 6D states. The line features observed in high resolution scans of the red-site
emission at 427.5 and 427.8 nm in Mn/Ar and Mn/ Kr, respectively, have been analyzed with the Wp optical line shape function and identified as resolved phonon structure originating from very weak sS=0.4d electron-phonon coupling. The presence of considerable hot-phonon emission seven in 12 K spectrad and the existence of crystal field splittings of 35 and 45 cmâ1 on the excited a 4D7/2
level in Ar and Kr matrices have been identified in Wp line shape fits. The measured matrix lifetimes for the narrow red-site a 6D state emissions s0.29 and 0.65 msd in Ar and Kr are much shorter than the calculated s3 sd gas phase value. With the lifetime of the metastable a 6D9/2 state shortened by four orders of magnitude in the solid rare gases, it is clear that the probability of the âforbiddenâ
a 6D!a 6S atomic transition is greatly enhanced in the solid state. A novel feature identified in the
present work is the large width and shifted 4D and 6D emissions produced for Mn atoms isolated in the blue sites of Ar and Kr. In contrast, these states produce narrow, unshifted sgas-phase-liked 4D and 6D state emissions from the red site.
||Luminescence spectroscopy, matrix-isolated z 6P, atomic
||Science & Engineering > Chemistry
Dr. John McCaffrey
||18 May 2007
|Journal or Publication Title:
||Journal of Chemical Physics
||American Institute of Physics
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