Luminescence spectra temperature dependence

Another example is the luminescence of in YPO4 with tetragonal zircon structure (Oomen et al. 1988). The emission consists of two bands, one in the UV region and one in the visible part of the spectrum. The intensity ratio of these bands is strongly temperature dependent (Fig. 5.57). 

Fig. 2. Temperature dependence of the homogeneous width (a) and the peak shift (b) of the 637 nm zero-phonon line in luminescence spectrum of N-V centers in diamond films points experiment the line theoretical approximations according to the laws y — y0 + aT3 + bT1 and 8 = fiT2 - vT4.

Although the previously observed phosphorescence of ferrocene now appears to have been artlfactual, a fairly strong luminescence has been observed from the analogous ruthenium(II) compound (53,210). The emission spectrum of ruthenocene, measured at low temperatures either from the pure solid or from glassy media, appears as a rather broad but highly structured band centered around a maximum at about 17 kK. The lifetime of the emission from the solid is strongly temperature dependent. 

Ru(dmb)j(decb) ] , [Ru(decb) (dmb) ], and (Ru(decb) (dmb -4,4 -dimethyl-2,2 -pyridine, decb 4,4 -bis(ethylcarboxy)-2,2 -bipyridine). Emission properties of [Ru(bpy) nH O and the circular dichroism spectrum of the excited state absorption of (a)-[Ru(bpy)3] have both been reported. The luminescence of Ru(II) and Os(II) polypyridyls has been measured in MeCN as a function of pressure and temperature, and it has been found that at high pressures the radiative and non-radiative transition rates between the luminescent CT level and the ground state are generally increased by 5-10%. Temperature dependence luminescence studies on [Ru(bpy) L] ... 

These phenomena can be explained by the occurrence of host-sensitized energy migration down to very low temperatures. The energy is trapped by uranate groups near defects (Fig. 13). When the temperature is raised, the uranate traps get emptied one by one, as follows from the temperature dependence of the zero-phonon lines in the emission spectrum. Now trapping at killer sites becomes also important this results in the temperature quenching of the luminescence. 

The fast decrease of the decay time of the luminescence of the (UO Vp) centre above about 60 K (Fig. 17) indicates that at higher temperatures a higher energy level becomes populated which has a considerably shorter life time than the A2 level. When the temperature dependence of the decay time is described in terms of a three level scheme, the data reveal that the higher energy level has a radiative decay time of about 5 ts. The temperature dependence of the relative intensities of the patterns associated with the two electronic origins in the emission spectrum and the... 

Fig. 8a-c Temperature dependence of the highest energy luminescence band of a [Gd(hfac)3NITBzImH] (solid lines) and [Eu(hfac)3NITBzImH] (dotted line, 5 K) b [Gd(NITBzImH)2(N03)3] (solid lines), [La(NITBzImH)2(N03)3] (dotted line, 5 K) c [Eu(NITBzImH)2(N03)3], absorption spectrum at 5 K shown as dotted line. Traces are offset along the ordinate for clarity... 

Fig. 12.19 a Temperature-dependent thermal luminescent spectrum of Rb2Sip6 Mn" phosphor and b relative intensity of emission spectrum by integrating the spectral area. Reproduced from Ref. [36] by permission of The Royal Society of Chemistry... 

Trindade N, Tabata A, Scalvi R, Scalvi L (2011) Temperature dependent luminescence spectra of synthetic and natural alexandrite (BeAl204 Cr ). Mater Sci Appl 2 284-287 Trofimov A (1962) The nature of linear luminescence spectrum in zircon. Geochemistry 11 972-975 (in Russian)... 

Drastic change takes place in luminescence spectrum of titanite at low temperatures (Fig. 4.80d). At 77 K, Nd luminescence intensity becomes lower and narrow line appears at 732 nm with long decay time of 2.5 ms accompanied by phonon repetitions. At even lower temperature of 20 K such emission totally dominates luminescence spectrum. Such behavior may be explained by Cr in intermediate crystal field sites for which the crystal field parameters lie in the crossing region of the T2 and states. Within the intermediate crystal field there is complicating mixing between doublet and quartet states with complicated spectra, non-radiative transfer and the temperature dependence of luminescence. In such case the emission from both T2 and E states may be expected. At 300 K the... 

The luminescence of Pb " " in synthetic Ca2ZnSi207 has been reported (Butler 1980). The emission and excitation peaks occur at 251 and 347 nm, respectively with a Stokes shift of 10,000 cm. It is very close to luminescence and excitation bands detected in natural samples. In order to prove the possible relation of the UV luminescence band at 355 nm to Pb in natural hardystonite, its decay time as a function of temperature has been studied. These decay curves are very specific for mercury-Uke ions, where the emission at low temperatures is ascribed to the forbidden transition Po- So and has a long decay time. Nevertheless, both Pi and Po are very close emitting levels so that at higher temperatures the luminescence from Pi level may appear with a similar spectrum, but with shorter decay (Boulon 1987 Blasse and Grabmaier 1994). In contrast, the decay times of the broad emissions of Ce or Eu are not temperature-dependent. At room temperature the decay time of the UV band in hardystonite at 355 nm in hardystonite is very short ( 25 ns). Nevertheless, with decreasing temperature a very long decay... 

---