Electromagnetic spectrum photons

A dye molecule has one or more absorption bands in the visible region of the electromagnetic spectrum (approximately 350-700 nm). After absorbing photons, the electronically excited molecules transfer to a more stable (triplet) state, which eventually emits photons (fluoresces) at a longer wavelength (composing three-level system.) The delay allows an inverted population to build up. Sometimes there are more than three levels. For example, the europium complex (Figure 18.15) has a four-level system. 

C07-0007. A compact disc player uses light of frequency 3.85 X lO s to read the information on the disc, (a) What is this light s wavelength (b) In what portion of the electromagnetic spectrum (visible, ultraviolet, and so on) does this wavelength fall (c) What is the energy of one mole of photons at this frequency ... 

C07-0059. Determine the wavelengths that hydrogen atoms absorb to reach the = 8 and n — 9 states from the ground state. In what region of the electromagnetic spectrum do these photons lie ... 

C07-0090. It requires 496 kJ/mol to break O2 molecules into atoms and 945 kJ/mol to break N2 molecules into atoms. Calculate the maximum wavelengths of light that can break these molecules apart. What part of the electromagnetic spectrum contains these photons ... 

Nonetheless, our primary interest lies in the 0.4 to 0.7 micron range, which we call the visible part of the electromagnetic spectrum. Note that even bodies at liquid-eiir temperatures emit photons between 10 and 100 microns in wavelength, i.e.- 100,000 and 10 A in wavelength. The earth itself at a temperature of 300 °K. has an emission between about 20,000 and 300,000 A... 

When a Rydberg atom reduces its principal quantum number by one unit, when emitting a photon, the light is in the microwave region of the electromagnetic spectrum. With this radiation isolated Rydberg atoms can be observed in interstellar space, where interatomic collisions are rare. Atoms with n up to 350 have been observed by radio astronomical methods. 

Figure 1.4 The electromagnetic spectrum, along with common photon sources and a number of characterization techniques based on photons.

Photons that are scattered, absorbed or emitted by a catalyst form a versatile source of information. Figure 1.4 shows the electromagnetic spectrum, along with a number of techniques involving photons. In addition to the common sources of photons (lamps, lasers, helium discharge and X-ray sources) available for laboratory... 

The energies of rotation are quite small, so we require photons of relatively low energy to photo-excite between rotational quantum levels. For this reason, the spacings between rotational energy levels correspond to transitions in the far infrared and microwave regions of the electromagnetic spectrum. 

It has been established beyond any reasonable doubt that the absorption and the emission of energy in the electromagnetic spectrum take place in distinct separate pockets or photons. The relationship... 

Most of us have encountered nuclear magnetic resonance (NMR) spectroscopy many times in the past, for example when analysing the products of preparative organic chemistry. In NMR spectroscopy, the nucleus of an atom is excited following absorption of a photon (in the radiofrequency region of the electromagnetic spectrum). 

---