Investigation of charge trapping in thin Kapton® polyimide films by means of photo-stimulated discharge spectroscopy
Photo-stimulated discharge-current spectroscopy was performed on 50 μm Kapton® 200HN polyimide thermo- and photoelectrets formed in the temperature range between −40ºC and +130ºC. Films were either charged in the DC electric field of 20 MV/m or photo-charged by illumination with light at the wavelength of 420 nm under the electric field of the same strength. Photocurrent spectra scanned in the wavelength interval 600–350 nm demonstrate a pronounced peak at approximately 470 nm revealing the presence of one charge-trapping level. The long-wavelength cut-off of the peak is at 550 nm corresponding to 2.3 eV trap depth.
The photoelectret state in kapton polyimide film. II. The effect of intensity of illumination and the autophotoelectret state
The photoelectret state in Kapton polyimide film as a function of intensity of illumination has been investigated using visible light and ultraviolet radiation. Experiments were carried out both with as-received and heat treated Kapton samples. The photoelectret charge is observed to increase with the intensity of illumination tending towards saturation which is in accordance with the reciprocity law. The nature of decay curves shows the presence of shallow and deep trap levels in Kapton. Ultraviolet radiations were found more efficient for photopolarization than visible light. Heat treatment results in reduction of photoelectret charge which may be due to the decrease in the number of traps owing to high temperature aging. The autophotoelectret state has also been investigated in Kapton. This study is useful for exploring the possibilities of using Kapton in electrophotographic process and solar energy conversion devices. 
 
 
 
Der Photoelektretzustand in Polyimidfilmen (Kapton) wurde in Abhangigkeit von der Intensitat der Beleuchtung mit sichtbarem und UV-Licht untersucht. Die Photoelektret-Ladung nimmt mit der Beleuchtungsintensitat zu und erreicht eine Sattigung in Ubereinstimmung mit dem Reziprozititatsgesetz. Die Zerfallskurven deuten auf die Existenz von flachen und tiefen Haftstellen (Traps) im Kapton hin. Ultraviolettstrahlung erwies sich hinsichtlich der Photopolarisation als wirksamer als sichtbares Licht. Warmebehandlung der Filme fuhrt zu einer Verringerung der Photoelektretladung, was auf einer Abnahme der Anzahl der Haftstellen beruhen kann. Weiter wurde der Autophotoelektretzustand im Kapton untersucht. Die Untersuchungen sind fur Anwendungen von Kapton in der Elektrophotographie und bei der Umwandlung von Solarenergie von Interesse.
The General Theory of Relativity
THE WORD “SPECIAL” IN “SPECIAL THEORY OF RELATIVITY” means that the theory is restricted to those frames of reference for which the law of inertia holds, that is, inertial frames of reference.* Einstein sometimes referred to them as Galilean frames of reference. At first glance, it does not seem reasonable to expect that the principle of relativity can be extended to non-inertial frames. The reasons are fairly obvious. The principle of relativity that we have been using states that the laws of physics have the same form in all frames of reference to which the principle applies. In other words there should be no way to determine by an experiment which of two frames of reference is in motion relative to the other.