Thermal diffusivity measurement using the mode-mismatched photothermal lens method

Analytical Model for Pulsed-Laser Induced Mode-Mismatched Dual-Beam Thermal Lens Spectroscopy in Liquids

“…Considering small phase shifts, the approximation exp(−iΦ) ≈ 1 − iΦ can be used, similar to the one performed by Shen et al 8 In this approximation, a simple analytical expression for a pulsed laser TL spectroscopy is given as follows: The limit of validity of this expression to describe the time evolution of the pulsed TL signal will be analyzed below. Note that for low absorption limit l eff (A e → 0) = l 0 , the (eq 15) becomes similar to the expression found by Marcano et al 18,19 The corresponding equation for a cw laser beam was reported by Shen et al 8…”

Approach to the Assessment of Size-Dependent Thermal Properties of Disperse Solutions: Time-Resolved Photothermal Lensing of Aqueous Pristine Fullerenes C60 and C70

“…Another challenge lies in the precision of transient thermal lensing governed by the geometry measurements that would require a wide-beam TLS technique. , Heat transfer from the viewpoint of material properties considers both the time-invariant heat transfer (governed by thermal diffusivity) and the dynamic (time-dependent) heat transfer (governed by thermal effusivity); we believe that it is important to estimate the effect of the particles on the thermal effusivity, i.e., the rate at which a sample absorbs heat. The above data lead us to the conclusion that AFDs produce nonequilibrium heat transfer due to their clustered character.…”

“…Still, such a dependence on the geometry is a serious drawback, and it should be overcome to increase the precision of measurements of thermal parameters. One of the most obvious solutions is the use of wide-beam schematics, which has been successfully applied so far. ,,, In this case, we can provide a longer time scale and much less dependence on the beam geometry and avoid any artifact effects due to slight changes in the geometry. This would also make the detection system less complex and make results more traceable.…”

Using optical tweezing to control phase separation and nucleation near a liquid–liquid critical point

“…Using the thermal conductivity of glass (k glass D 1 W m À1 K À1 ), the specific heat capacity nitrobenzene (c p,nitrobenzene = 1400 J kg À1 K À1 ), the mass density of nitrobenzene (r nitrobenzene = 1175 kg m À3 ), the thickness of the windows used in the experiments (d glass = 80 mm), it is found that b = 507 Hz. Using the thermal diffusivity of nitrobenzene 47 (a nitrobenzene = 0.94 Â 10 À7 m 2 s À1 ) and eqn (20), we can calculate the stationary heating spot radius (at 1/e of the maximum) as Oa/b = 13 mm for a glass window (and Oa/b = 16 mm for a mica window). This is significantly larger than the beam radius (see below), justifying the delta-function heat-source approximation.…”