Collier Martin A, Ryan Maryanne C, McCaffrey John G
Department of Chemistry, National University of Ireland-Maynooth, Maynooth, County Kildare, Ireland.
J Chem Phys. 2005 Jul 22;123(4):044508. doi: 10.1063/1.1961531.
Laser-induced excitation spectra recorded for the electric-quadrupole 3d(6)4s a6D(J)<--3d(5)4s2a6S(5/2) transitions of atomic Mn, allow assignment of the red emission features, previously observed in Mn/RG (RG=Ar, Kr and Xe) matrices with resonance 3d(5)4s4pz6P(5/2)<--3d(5)4s2 a6S(5/2) excitation, to the metastable a6D(9/2) state. Narrow excitation bands recorded for the red site in the Mn/Kr system allow identification of all five spin-orbit levels (J=1/2, 3/2, 5/2, 7/2 and 9/2) in the a6D state. The coincidence of the lowest energy excitation band and the observed 585.75 nm (17,072 cm(-1)) emission band of atomic Mn in Kr matrices, yielded a definitive assignment of this emission to a transition from the J=9/2 spin-orbit level. Temperature dependent emission scans lead to the identification of the zero phonon line for the a6D(9/2)-->a6S(5/2) transition at 585.75 nm. The identified matrix-shift of +20 cm(-1) allows an assessment of the extent of the ground state stabilization in the red (secondary) site of atomic Mn isolation in solid Kr. Emission produced with direct a6D state excitation yielded both the 585.75 and 626 nm features. The former band arises for Mn atoms occupying the red site--the latter from blue site occupancy in solid Kr. The excitation linewidths recorded for these two sites differ greatly, with the blue site yielding a broad featureless profile, in contrast to the narrow, structured features of the red site. The corresponding red site a6D(J)<-->a6S(5/2) transitions in Ar and Xe matrices are broader than in Kr--a difference considered to originate from the site sizes available in these hosts and the interatomic Mn x RG potentials. The millisecond decay times recorded for the red emission bands in the Mn/RG systems are all much shorter than the 3 s value predicted for the gas phase a6D(9/2)-->a6S(5/2) transition. This enhancement allows optical pumping of the forbidden a6D(J)<-->a6S transitions with low laser powers when atomic manganese is isolated in the solid state. However all the emission decays are complex, exhibiting triple exponential decays. This behavior may be related to the dependence of the excitation linewidths on the J value, indicating removal of the J degeneracy due to weak matrix-induced, crystal field splitting.
记录的原子锰电四极矩3d(6)4s a6D(J)<--3d(5)4s2 a6S(5/2)跃迁的激光诱导激发光谱，使得先前在Mn/RG（RG = Ar、Kr和Xe）基质中通过共振3d(5)4s4pz 6P(5/2)<--3d(5)4s2 a6S(5/2)激发观察到的红色发射特征，被归属于亚稳态a6D(9/2)态。在Mn/Kr系统中为红色位点记录的窄激发带，使得能够识别a6D态中的所有五个自旋轨道能级（J = 1/2、3/2、5/2、7/2和9/2）。最低能量激发带与在Kr基质中观察到的原子锰585.75 nm（17,072 cm(-1)）发射带的重合，明确将该发射归属于从J = 9/2自旋轨道能级的跃迁。温度依赖的发射扫描导致识别出在585.75 nm处a6D(9/2)-->a6S(5/2)跃迁的零声子线。所识别的+20 cm(-1)的基质位移，使得能够评估固态Kr中原子锰隔离的红色（二级）位点基态稳定化的程度。直接a6D态激发产生的发射产生了585.75和626 nm的特征。前一个带源于占据红色位点的锰原子——后一个带源于固态Kr中蓝色位点的占据。为这两个位点记录的激发线宽差异很大，蓝色位点产生宽的无特征谱形，与红色位点窄的、有结构的特征形成对比。在Ar和Xe基质中相应的红色位点a6D(J)<-->a6S(5/2)跃迁比在Kr中更宽——这种差异被认为源于这些主体中可用的位点大小以及原子间Mn x RG势。在Mn/RG系统中为红色发射带记录的毫秒级衰减时间，都比气相a6D(9/2)-->a6S(5/2)跃迁预测的3 s值短得多。这种增强使得当原子锰在固态中隔离时，能够用低激光功率对禁戒的a6D(J)<-->a6S跃迁进行光泵浦。然而所有的发射衰减都是复杂的，表现出三重指数衰减。这种行为可能与激发线宽对J值的依赖性有关，表明由于弱的基质诱导的晶体场分裂导致J简并的消除。
