Optical metastability

Electronically excited halogen atoms in the np5 2P% state are optically metastable as the transition... 

A phenomenon which is related to the PPC effects is the optical metastability in GaN. Optical metastability has been observed in GaN epilayers and InGaN/GaN multiple quantum wells [24-26]. Optical metastability in bulk GaN was manifested by a photoinduced decrease in the output intensity of the bandedge transition at 365 nm followed by an increase in the output intensity of a new emission band at 378 nm [25], The recovery time associated with the observed optical metastability is very long (weeks). The cause for such an effect was attributed to the presence of traps in bulk GaN [25], In... 

Laser transitions operating with the 5 state of Se as the upper level are currently of interest, as the possibility of storing considerable amounts of energy in this optically metastable state implies that high-power pulsed output on the and transitions at 776.8 and 488.7nm will result. Photolysis of... 

The characteristic field, at which the Bragg band disappears, is considerably higher than the critical field ( = 7 V/pm) calculated from the thermodynamic approach, see Eq. (12.29). However, the periodic structure with very thin defect walls separating area of opposite director orientation (

helical structures are also observed at field strengths > in experiments with short voltage pulses when the defects have not enough time to form. 

In a sector instrument, which acts as a combined mass/velocity filter, this difference in forward velocity is used to effect a separation of normal and metastable mj" ions (see Chapter 24, Ion Optics of Magnetic/Electric-Sector Mass Spectrometers ). However, as discussed above, the velocity difference is of no consequence to the quadmpole instrument, which acts only as a mass filter, so the normal and metastable mj ions formed in the first field-free region (Figure 33.1) are not differentiated. 

By adjusting magnetic and electric fields in the ion optics (see Chapters 33 and 34 on linked scanning), metastable ions can be investigated. 

The facile insertion of carbodiimides into a Ti-CMe bond of (CsRslTiMes (R = FI, Me) (cf. Section 1II.B.2) has been extended to the insertion of optically pure (R,R)- and meso-(R,S)-1.3-bis(l-phenylethyl)carbodiimide. Treatment of Cp M(NMe2)3 (M = Zr, FFf) with both achiral and optically pure aminooxazoline proligands ITL yielded metastable aminooxazoline half-sandwich diamide... 

Fe(ptz)6] (BF4)2 and [Zni Fej.(ptz)6] (BF4,)2. The solid iron(II) complex of the unidentate ligand ptz = 1-propyltetrazole shows a reasonably sharp spin-state transition at about 130 K [112]. Optical excitation into the spin-allowed -> absorption band produces via LIESST the HS T2 state which remains trapped at temperatures below 50 K. Relaxation of the metastable J2 state to the LS state has been studied by following the changes of... 

Photolysis of DAX in a methylcyclohexane glass at 77 K creates a metastable species detected by its optical absorption spectrum (Table 4). This solution does not exhibit an epr spectrum characteristic of a triplet carbene, nor is one observed when DAX is irradiated in Fluorolube (where triplet carbenes are generally more stable). Warming the frozen solution causes the reaction of the metastable transient and the formation of dimeric xanthone azine. 

Closely related to the metastable ion structure is the determination of kinetic energy release, which appears as a rather sensitive probe to reaction dynamics3-5. However, a comprehensive analysis of the kinetic energy release is in general a complicated process and requires detailed information regarding the ion-optic system3-5. 

V.V. Atuchin, I. Savatinova, C.C. Ziling, High refractive index metastable phases in proton exchanged H LiTa03 optical waveguides, Mat. Lett. 46, 189-192 (2000). 

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