In contrast to the usual spectroscopic methods, the temperature of a gas embedded in a tube was measured here and not the intensity loss of the radiation. In order to minimize the interference by the tube, light-weight building materials were used, preferably Styrofoam, transparent plastic foils and aluminium foils. Sunlight as well as infrared (IR)-bulbs was employed as radiation sources, whereby near-IR is predominant and not medium-IR as it is usually assumed. Different gases were tested, not only air and carbon-dioxide but also the noble gases argon, helium and neon. In each case, a temperature increase was detected up to a limiting value. While the warming-up rate was independent of the gas type, the limiting temperature turned out to be gas-specific. Surprisingly and contrary to the expectation of the greenhouse theory, the limiting temperatures of air, pure carbon-dioxide and argon were nearly equal while the light gases neon, and particularly helium, exhibited significant lower limiting temperatures. Applying the kinetic gas theory, and assuming a direct correlation between limiting temperature and radiative emission power, a stringent dependency of the product on mean kinetic energy and collision frequency could be deduced. Moreover, the adsorption degree could be calculated, turning out to be very low. The absorption was assumed as a result of vibration of the atomic electron shell, induced by the electromagnetic waves. Comparing the results in sunlight to those obtained in artificial light, the effective wavelength could be assessed delivering the value of 1.9 μm. Therefore, the greenhouse theory has to be questioned.
Key words: Solar-tube, gas-temperature, radiation-absorption, radiation-emission, kinetic-gas-theory, near-infrared, carbon-dioxide.
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