Lattice temperature

Herber, R.H. Stmcture, bonding and the Mossbauer lattice temperature. In Berber, R.H. (ed.) Chemical Mossbauer Spectroscopy. Plenum, New York (1984)... 

The description of these apparatus is beyond the scopes of this book. The reader is referred to the exhaustive treatment of this subject for example in ref. [22,32]. Just to get an idea of the capabilities of this method see ref. [33], where a refrigerator capable of maintaining lattice temperatures below 100p,K for two months is described. 

Situations that depart from thermodynamic equilibrium in general do so in two ways the relative concentrations of different species that can interconvert are not equilibrated at a given position in space, and the various chemical potentials are spatially nonuniform. In this section we shall consider the first type of nonequilibrium by itself, and examine how the rates of the various possible reactions depend on the various concentrations and the lattice temperature. 

Semimetals bismuth (Bi) and antimony (Sb) have been model systems for coherent phonon studies. They both have an A7 crystalline structure and sustain two Raman active optical phonon modes of A g and Eg symmetries (Fig. 2.4). Their pump-induced reflectivity change, shown in Fig. 2.7, consists of oscillatory (ARosc) and non-oscillatory (ARnonosc) components. ARosc is dominated by the coherent nuclear motion of the A g and Eg symmetries, while Af nonosc is attributed to the modification in the electronic and the lattice temperatures. 

Figure 3.43. The time dependent electronic temperature Te, lattice temperature Tq. and adsorbate temperature defined as Tads = [EH /2kB following a 130 fs laser pulse with absorbed laser fluence of 120 J/m2 centered at time t = 0. The bar graph is the rate of associative desorption dY/dt as a function of t. Te and T are from the conventional two temperature model and 7 ads and dY/dl are from 3D first principles molecular dynamics with electronic frictions. From Ref. [101].

Hence, if the crystal is initially in a magnetically ordered state at (lattice) temperature T (hot lattice + cold spins), but is then demagnetized under adiabatic conditions (q = 0), the entropy of spin disordering must be drawn from the crystal lattice (because no heat can exchange with the surroundings), and the lattice temperature drops ... 

On implantation into the cold foil the nuclei are initially fhot i.e. unpolarised. They approach thermal equilibrium with the foil lattice temperature through the Korringa relaxation mechanism via the conduction electrons. 

The two-temperature equation is used to characterize mutual interactions among lattice temperature, and number density and temperature of carriers during pico- to femtosecond pulse laser processing [12]. In this study, a new parameter related with non- equilibrium durability is introduced and its characteristics for various laser pulses and fluences are discussed. 

Figure 5 (a) carrier and lattice temperatures and (b) carrier number densities for different laser fluences at the silicon layer front surface when A, = 530 ran and = 60 ps [12]... 

The influence of laser fluence and pulse duration time on microscale heat tiansfer mechanisms are investigated by using one-dimensional said transient equations of eerier and lattice temperatures. The scale difference between energy relaxation and laser pulse duration times results in file fiiermal non-equilibriimi state fiiat can be controlled by laser fluence as well as pulse dmation time. In the case fiiat a few picosecond pulse laser is irradiated over file semiconductor surface with relatively hi fluence, a two-peak structme in file carrier temperature variation can be observed. As pulse dmation increases, file m imiun eerier temperature and file number density decrease, whereas file lattice temperature is nearly of constant values. Meanwhile, the two-peak structme due to Auger heating disappears and converts into the one-peak stinctme as file laser fluence decreases. 

Eesley, G.L. Generation of nonequilibrium electron and lattice temperatures in copper by picosecond laser pulses. Phys. Rev. B 33, 2144-2151 (1986)... 

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