Patent ID: 7542140

Claim:
A method of detecting a state change of a substance using an electromagnetic wave selected from a frequency range of 0.1 THz to 10 THz, comprising: a first step of placing a substance on a sample holding section; a second step of irradiating the substance with the electromagnetic wave; a third step of detecting an electromagnetic wave that has passed through or been reflected from the substance; a fourth step of determining a frequency dependence of a property of the substance with respect to the irradiating electromagnetic wave from information about the detected electromagnetic wave and the irradiating electromagnetic wave and then calculating a slope of a straight line or a slope of a straight line obtained by straight-line approximation of the frequency dependence of the property of the substance; and a fifth step of evaluating a degree of state change from a standard state of the substance by comparing a previously-obtained slope of a straight line of the frequency dependence of the property of the substance in the standard state and the slope of the straight line of the substance calculated in the fourth step.