Steady State ODMR

The detail of our experimental apparatus used in the steady state ODMR experiment is given in Morigaki et al. (1983). 

Ahl- eneigy of the high energy edge of the luminescence spectrum, i/u. energy of the low energy edge of the luminescence spectrum. 

The ODMR spectra are dependent on various experimental conditions, 

According to the theoretical considerations given in Part II, those two lines (Di and Dj) are identified as being due to nonradiative centers. Furthermore, the g-value of the D2 line coincides with that of dangling-bond centers in a-Si (the dark ESR signal), i.e., 2.0055 (Brodsky and Title, 1969), so that the D2 center is attributed to a dangling-bond center. The A line is observed as an 

The intensity of ODMR signals is proportional to a change in the luminescence intensity A/ at resonance. The quantity A/ divided by the luminescence intensity / is used to characterize the spectral dependence of the 

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The common requirement for each steady-state ODMR detection method is the presence of population differences between saturated sub-levels. If the steady-state populations of a pair of sublevels happen to be equal, for instance, an electron-electron double resonance... 

The technique of microwave-recovery provides crucial information about the substates involved in the ODMR transitions. For this experiment, Pd(2-thpy)2 is optically excited by a c. w. source. This leads to specific populations of the three triplet substates. At low temperature, they are thermally decoupled and thus emit according to their specific populations and their individual decay constants (e. g. see Sect. 3.1.3 and Table 2). In the microwave recovery experiment, the steady state conditions are perturbed by a microwave pulse being in resonance with the zero-field transition at 2886 MHz. Due to the microwave pulse, the populations of the two states involved are changed. Subsequently, one monitors the recovery of the emission intensity in time until the steady state situation is reached again. The microwave pulses have, for example, a duration of 20 ps and are applied repeatedly to enable a detection with signal averaging [61]. 

A slow-passage ODMR measurement is carried out ideally when the microwave passage time through magnetic resonance is very much slower than the triplet sublevel lifetimes. The steady-state solutions of Eqs. 

The ODMR signal intensity associated with the steady-state population changes depends on the detection method. The absorbance changes in ADMR are proportional to changes in Nj and may be expressed as... 

Here Ay is a double index that stands for full-field A y( -I-, 0) and (0, -) and half-field (-I-, -) resonances, respectively AN is their respective steady-state population difference (A N+.o = N+ - N(),etc.)for/x waveoff and A/ is the difference in the respective recombination rales (AR + o = R+ - Ro, etc.). From Eq. (29) we see that SN can be of either sign or even zero, depending on AN and AR. Due to the above complexity of unther-malized spin polarization, LESR, ADMR, and PL-ODMR triplet powder patterns are much more complicated than their ground-state (thermalized) ESR counterparts. Enhancing and reduction features and even derivative-like line shapes may exist in ODMR triplet powder patterns. 

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