Long wavelength radiation

The same UV lamps discussed in Section 2.2.3.1 are employed to excite fluorescence. Excitation is usually performed using long-wavelength radiation (2 = 365 nm), shorter wavelengths are occasionally employed (e.g. 2 = 302 nm, DNA analysis). 

The wavelength is rather long— 3.40 m—but radio waves are known as long wavelength radiation. See Figure TA for a sense of the wavelengths of electromagnetic radiation. 

Greenhouse effect Atmospheric gases trap long-wavelength radiation emitted by a planet, resulting in an increased surface temperature. 

FIGURE 14-5 Annual mean radiation measured by satellite in 1988 at the top of the atmosphere as a function of latitude for incoming absorbed short-wavelength radiation and emitted outgoing long-wavelength radiation (adapted from Trenberth and Solomon, 1994). 

These weaker bands can have significant effects on the calculated outgoing infrared radiation. For example, Ho et al. (1998) show that much of the reported discrepancy between modeled outgoing long-wavelength radiation and satellite measurements can be attributed to not including weaker absorption bands due to C02 at 4.3 /xrn and 03 at 14 pm and the weaker O, lines located far from the center of the strong 9.6-pm band. 

The color of light depends on its frequency or wavelength long-wavelength radiation has a lower frequency than short-wavelength radiation. 

Carrying the analogy between the photochemistry of Fe(C0)ij and Fe(C0)3[l,4-Me2N4] one step further we note that both compounds (25,26) behave as photoassisted olefin hydrosilation and isomerization catalysts. One distinction between the two catalyst systems is the latter (26) operates effectively with long wavelength radiation, Table II. Hydrosilation activity requires continuous photolysis ... 

It is important to note at this point that the blackness of a surface-to-thermal radiation can be quite deceiving insofar as visual observations are concerned. A surface coated with lampblack appears black to the eye and turns out to be black for the thermal-radiation spectrum. On the other hand, snow and ice appear quite bright to the eye but are essentially black for long-wavelength thermal radiation. Many white paints are also essentially black for long-wavelength radiation. This point will be discussed further in later sections. 

At radiation equilibrium the net energy absorbed from the sun must equal the long-wavelength radiation exchange with the surroundings, or... 

A large surface has a = 0.6 for long-wavelength radiation and a = 0.95 for solar radiation. Calculate the radiation equilibrium temperature of the surface if its back side is insulated and top side is exposed to a solar radiation flux of 950 W/m2 and an environment at 300 K with h = 12 W/m2 °C. 

In contradiction to earlier findings it has been pointed out - that luminescence is not restricted to excitation by long-wavelength radiation. A slight luminescence could be observed also at excitation wavelengths of 2537 A or even less. 

Novel sample preparation techniques include ultrasonic extractions that use high frequency acoustic waves to heat and break up samples (9), as well as microwave-assisted extractions (MAE) that use long wavelength radiation for faster and less energy intensive extractions of thermally sensitive analytes (JO-13). Other innovations treat samples with high pressure and high temperature solvents in the liquid or in the supercritical state. These adaptations reduce the overall solvent use and speed the extractions. These methods include accelerated solvent extraction (ASE) (14) and supercritical fluid extraction (SEE) (8). 

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