Solar power spectrum

The solar spectrum corresponds roughly to the radiation of a black body at the temperature 5750 K. If we denote the photon flux in the wavelength interval from A to (A 4- dA) (in photons/m2 s) as /(A), the total solar power flux (in W/m2) is given as ... 

Figure 1. The power spectrum analysis of Guthrie and Napier s first sample of 97 redshifts. This peak power occurs when redshifts are corrected for the solar motion with respect to our galactic center.

A successful garden represents a broad spectrum of chemical processes. Photosynthesis provides the route by which diverse chemical transformations use sunlight, water, carbon dioxide, and inorganic chemical elements to produce life-sustaining organic molecules and oxygen (Equation 1). This solar-powered rearrangement of matter is the foundation of almost all ecosystems and is an important example of how chemistry applies to the study of life. 

This relation is known as Wien s displacement law, and it provides a convenient means of determining where the wavelength of peak radiated energy occurs for a given temperature. For example, the solar radiation spectrum has a peak at about X = 0.5 pm, as Tmn = 5762 K. On the other hand, an object at room temperature (Troom = 300 K) would emit maximum energy at about X = 10 pm. It is obvious that, as absolute temperature increases, the wavelength at which the maximum emissive power occurs becomes smaller. 

Transient absorption (TA) spectroscopy has greatly improved our understanding of solar-powered devices, particularly in the areas of photocatalysis and photovoltaics using Ti02- In the technique, a pump pulse, typically from a laser, places the sample in an excited state with new electronic and/or chemical properties. A time-delayed probe pulse measures the absorption spectrum of the sample after it is altered by the first pulse. Measuring the change in absorption compared to the initial value as a function of the delay between the pulses gives the dynamics of the system (Fig. 2). 

The band-gap excitation of semiconductor electrodes brings two practical problems for photoelectrochemical solar energy conversion (1) Most of the useful semiconductors have relatively wide band gaps, hence they can be excited only by ultraviolet radiation, whose proportion in the solar spectrum is rather low. (2) the photogenerated minority charge carriers in these semiconductors possess a high oxidative or reductive power to cause a rapid photocorrosion. 

The spectrum in both the optical and the ultraviolet at about two days is fairly well represented by a hydrogen envelope with a power law density profile (p r11) of one-quarter solar metaiiiclty in LTE. Theoretical spectra at this early epoch tend to favor luminosities on the high side of observational estimates in order to ionize Ca II and prevent excessively strong lines at H and K and the infrared triplet, with some ramifications for distance estimates. 

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