Abstract: A method for controlling the emission frequency of a laser comprises: recording a first spectrum by passing a laser light emitted by the laser through a sample onto a detector, the detector being connected to a multichannel analyzer which assigns pulses detected by the detector to a channel; determining a first channel to which the maximum of a first signal in the first spectrum has been assigned; determining a second channel to which the maximum of a second signal in the first spectrum has been assigned; recording a second spectrum in analog fashion like the first spectrum; determining whether the maximum of the first signal in the second spectrum has been assigned to the first channel and whether the maximum of the second signal in the second spectrum has been assigned to the second channel; adjusting the operating temperature of the laser in the event of deviations determined in the previous step.

Abstract: A method for controlling the emission frequency of a laser comprises: recording a first spectrum by passing a laser light emitted by the laser through a sample onto a detector, the detector being connected to a multichannel analyzer which assigns pulses detected by the detector to a channel; determining a first channel to which the maximum of a first signal in the first spectrum has been assigned; determining a second channel to which the maximum of a second signal in the first spectrum has been assigned; recording a second spectrum in analog fashion like the first spectrum; determining whether the maximum of the first signal in the second spectrum has been assigned to the first channel and whether the maximum of the second signal in the second spectrum has been assigned to the second channel; adjusting the operating temperature of the laser in the event of deviations determined in the previous step.

Abstract: The invention relates to a long path cell (10), in particular a Herriott cell, with (a) a primary mirror (12) and (b) a secondary mirror (14). According to the invention, it is provided that the primary mirror (12) has a first primary mirror segment (42.1) and at least one second primary mirror segment (42.2), which radially surrounds the first primary mirror segment (42.1), whereby the primary mirror segments (42) differ in their curvatures (R42.1, 42.2) or focal lengths, the secondary mirror (14) has a first secondary mirror segment (44.1) and at least one second secondary mirror segment (44.2) which radially sur-rounds the first secondary mirror segment (44.1), whereby the secondary mirror segments (44) differ in their curvatures (R42.1, R42.2) or focal lengths, the first primary mirror segment (42.1) and the first secondary mirror segment (44.1) are arranged in relation to each other such that a light beam is reflected back and forth between the two, and that the second primary mirror segment (42.

Abstract: The invention relates to a long path cell (10), in particular a Herriott cell, with (a) a primary minor (12) and (b) a secondary mirror (14). According to the invention, it is provided that the primary mirror (12) has a first primary minor segment (42.1) and at least one second primary minor segment (42.2), which radially surrounds the first primary mirror segment (42.1), whereby the primary minor segments (42) differ in their curvatures (R42.1, 42.2) or focal lengths, the secondary minor (14) has a first secondary minor segment (44.1) and at least one second secondary mirror segment (44.2) which radially sur-rounds the first secondary minor segment (44.1), whereby the secondary minor segments (44) differ in their curvatures (R42.1, R42.2) or focal lengths, the first primary mirror segment (42.1) and the first secondary minor segment (44.1) are arranged in relation to each other such that a light beam is reflected back and forth between the two, and that the second primary mirror segment (42.

Abstract: A method for determining the temperature of an infrared-active gas by means of infrared spectroscopy is provided. The method comprising: radiating infrared light in a spectral range of 700 cm?1 to 5000 cm?1 originating from an infrared light source onto the gas; obtaining a first absorption-related parameter originating from measuring a first infrared absorption band of the gas, wherein the first infrared absorption band is a hot band being caused by thermal population of at least one vibrational mode of the gas; obtaining a second absorption-related parameter originating from measuring a second infrared absorption band of the gas, and calculating a ratio between the first absorption-related parameter and the second absorption-related parameter. The method is characterized in that the ratio is used to determine the temperature of the gas, wherein the ratio has a relative change of at least 0.5% per Kelvin temperature difference of the gas.

Abstract: A method for determining the metabolic capacity of an enzyme includes time-resolved determination of the concentration of a product in exhaled air. The product is created by metabolism of a substrate, previously administered to an individual, by an enzyme of the individual. The product concentration is determined until the maximum product concentration in the exhaled air is reached. A model function is fitted to measured values of the product concentration, obtained by the time-resolved determination of the product concentration between start and end times. The metabolic capacity of the enzyme is determined based on parameters of the model function. Determining the metabolic capacity of the enzyme takes place based on at least two parameters of the model function, wherein the maximum value and time constant of the model function are not selected as parameters at the same time, and the start and/or end times are not selected as parameters.

Abstract: A measurement device and a method for analyzing a sample gas by infrared absorption spectroscopy are described. The measurement device comprises a narrowband laser having a line width of less than 0.2 cm?1 and being smaller than a width of an infrared absorption line to be measured of a sample gas. The measurement device is suited and can be arranged to measure the respiratory gas of a human or animal as sample gas, wherein the respiratory gas exchanges in the measurement chamber only by the respiration of the human or animal, and the respiratory resistance of the measurement device is less than 60 mbar.

Abstract: A method for determining the metabolic capacity of an enzyme includes time-resolved determination of the concentration of a product in exhaled air. The product is created by metabolism of a substrate, previously administered to an individual, by an enzyme of the individual. The product concentration is determined until the maximum product concentration in the exhaled air is reached. A model function is fitted to measured values of the product concentration, obtained by the time-resolved determination of the product concentration between start and end times. The metabolic capacity of the enzyme is determined based on parameters of the model function. Determining the metabolic capacity of the enzyme takes place based on at least two parameters of the model function, wherein the maximum value and time constant of the model function are not selected as parameters at the same time, and the start and/or end times are not selected as parameters.

Abstract: A method for determining the 14C content of a gas mixture in which 14C isotopes are present as molecule constituents, is provided. The gas mixture is provided in a measuring space, wherein infrared laser radiation is supplied to the measuring space as measurement radiation. The laser radiation to be supplied to the measuring space is deflected such that it passes through the measuring space a plurality of times by interacting with the gas mixture, wherein the laser radiation is supplied to a detector, in order to determine the absorption of laser radiation by the gas mixture and therefrom determine the 14C content. For generating the laser radiation a pulsed laser is used, which as measurement radiation emits laser pulses with a pulse duration of less than 5 ?s, which are supplied to the measuring space.

Abstract: A measurement device and a method for analyzing a sample gas by infrared absorption spectroscopy are described. The measurement device comprises: a measurement chamber with the sample gas to be analyzed, a laser being arranged in relation to the measurement chamber such that light being emitted from the laser radiates through the measurement chamber, a detection device detecting the light being emitted from the laser and radiated through the measurement chamber, and an evaluation unit evaluating signals generated by the detection device regarding a light absorption occurred in the measurement chamber.