Microwave photon

From comparison of the data presented in Table 2.2 [8], it is obvious that the energy of the microwave photon at a frequency of 2.45 GHz (0.0016 eV) is too low to cleave molecular bonds and is also lower than Brownian motion. It is therefore clear that microwaves cannot induce chemical reactions by direct absorption of electromagnetic energy, as opposed to ultraviolet and visible radiation (photochemistry). 

It is well known that y or X photons have energies suitable for excitation of inner electrons. We can use ultraviolet and visible radiation to initiate chemical reactions (photochemistry). Infrared radiation excites bond vibrations only whereas hyperfrequencies excite molecular rotation. In Tab. 1.1 the energies associated with chemical bonds and Brownian motion are compared with the microwave photon corresponding to the frequency used in microwave heating systems such as domestic and industrial ovens (2.45 GHz, 12.22 cm). 

According to these values, the microwave photon is not sufficiently energetic to break hydrogen bonds. Its energy is, furthermore, much smaller than that of Brow-... 

Irradiation of food inside the microwave oven causes photon uptake. The energy liberated each time a photon is absorbed is not sufficient to cause bond breakage (as was the case with UV light) nor can these microwave photons cause excitation of electrons (which is why we see a colour during irradiation with visible light but not with microwaves). Again, the energy is insufficient to... 

What is the energy of a single microwave photon Take X = 1 cm. 

Because the coefficients of absorbance and emission are identical, a microwave photon of the appropriate frequency would be equally likely to cause emission of an identical photon from an excited molecule as to be absorbed by a molecule in the ground state if equal numbers of molecules were present in each state. Therefore, net absorbance of energy depends on the difference in populations between the ground state and the excited state. 

Fig. 10.19 The microwave frequency dependence of the n changing signals at low microwave power, where n changes up or down only by 1. Resonant multiphoton transitions are observed near the expected static field Stark shifted frequencies indicated. These resonances involve the absorption of four or five microwave photons. The down n changing atom production curve was obtained with the state analyzer field EA set at 50.0 V/cm, while up n changing was studied as n = 60 atom loss with EA = 45.5 V/cm. The locations of resonances for larger direct (not stepwise) changes in n are indicated along with...

To place these results in context it should be reaffirmed that microwave heating is a completely distinct phenomenon operating in an entirely different way from microwave spectroscopy. This latter process involves the direct interaction of photons of a particular energy in order to excite the quantum rotational levels of gas-phase sample. Although in microwave heating, the absorption of microwave irradiation by a sample has been shown to be frequency dependent, it is not a requirement of the system for the energy to be quantised. As a result the heating process does not depend upon the direct absorption of microwave photons, instead the sample is heated via... 

A molecule can only absorb infrared radiation if the vibration changes the dipole moment. Homonuclear diatomic molecules (such as N2) have no dipole moment no matter how much the atoms are separated, so they have no infrared spectra, just as they had no microwave spectra. They still have rotational and vibrational energy levels it is just that absorption of one infrared or microwave photon will not excite transitions between those levels. Heteronuclear diatomics (such as CO or HC1) absorb infrared radiation. All polyatomic molecules (three or more atoms) also absorb infrared radiation, because there are always some vibrations which create a dipole moment. For example, the bending modes of carbon dioxide make the molecule nonlinear and create a dipole moment, hence CO2 can absorb infrared radiation. 

Let us quote the text from Ref. [15] "...a, Quantum eraser configuration in which electro-optic shutters separate microwave photons in two cavities from the thin-film semiconductor (detector wall) which absorbs microwave photons and acts as a photodetector, b, Density of particles on the screen depending upon whether a photocount is observed in the detector wall ( yes ) or not ( no ), demonstrating that correlations between event on the screen and the eraser photocount are necessary to retrieve the interference pattern."... 

In this section we consider the interaction between nnclear motion in mole-cnles and infrared and microwave photons. 

As shown by Fig. 8 we can see collisions in which stimulated emission of up to three microwave photons occurs using very low microwave powers. It is interesting to note that laser assisted collisions typically require optical intensities of MW/cm2 to be visible at all [Falcone 1977], In Fig. 8 it appears that the one photon assisted collision disappears only to reappear at higher microwave fields. This unexpected feature becomes more apparent if we plot the resonance signal vs the microwave field, as shown in Fig. 9. Also shown by the lines in Fig. 9 are the results of a model describing collisions in which from zero to three photons are emitted. 

One frontier for current exploration concerns the nucleosynthesis occurring in the Universe s dark ages between the time the cosmic microwave photons were set free and systems containing normal stars had formed. In this connection, I close with an extensive quotation from Fred Hoyle s Frontiers of Astronomy ... 

Advanced sensor technologies with application to detection and clearance can be grouped as follows infrared sensors, ground-penetrating radars, microwave, photon backscatter, nuclear or thermal neutron analysis, and lasers. Their characteristics were summarized in Table 12.1. 

Enormous numbers of microwave photons are needed to warm macroscopic samples of matter. A portion of soup containing 252 g of water is heated in a microwave oven from... 

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