TABLE 1.

Optical properties at 337 nm and thermal properties of cells, histologic material, polyethylene naphthalate polymer foil, glass, and water

Material	Sample thickness x (μm)	Transmission (%)	Extinction coefficient μeff (cm−1)	Optical penetration depth δ (μm)	Average heat capacity (kJ K−1 kg−1)	Phase transition temperature (°C)	Heat conductivity (W m−1 K−1)	Density (kg m−3)
Glass slide	1000	94.7	0.55	18200	0.666	—	1.07	2500
PEN*-foil	1.35	T = 20.5 R = 22.4	μa = 3520 μ′s = 8680 μeff = 11360	0.88	2.7	460	≈0.4	1.39
H&E† stained histol. specimen	≈5	7–35 (15.7)	2100–5300 (3700)	1.9–4.8 (2.7)	3.2	340	≈0.5	≈1000
CHO‡ cells	≈5	93.8	127	79	4.0	150–300		≈1000
Water			0.0172	5.8 × 105	4.187	300	0.598	998

All transmission data are corrected for specular reflection, i.e., they represent purely the transmission of the sample. The optical parameters for stained histologic specimen cover a certain range given by variations in staining. The values in brackets were used for the temperature calculation in the Discussion. Sources for data not measured in this study are: for water absorption (25), for heat conductivity, heat capacity, and density of water, glass, PEN, and Teflon (77), and for the density of PEN: www.m-petfilm.com. The phase transition temperature corresponds for PEN to the temperature at which photothermal dissociation into gaseous components occurs, for water to the superheat limit in bubble-free liquid water (24), and for cells to their heterogeneous nucleation threshold above which the cell is destroyed by vapor bubble formation around nucleation centers within the cell (78,79). Due to the short heat exposure time, bubble formation rather than thermal denaturation constitutes the damage threshold for cells (79).

^*Polyethylene naphthalate.

^†Hematoxilin and eosin.

^‡Chinese hamster ovary.