Abstract: A pulse shaper for compensating group runtime effects is provided. The pulse shaper comprising a first and a second dispersive element. An optical pulse can be coupled to the pulse shaper along a coupling direction such that said pulse exits from the pulse shaper after passing through the first and the second dispersive element along an exit direction. The first and the second dispersive element are formed and arranged to be movable relative to each other such that the path length to be traversed by the optical pulse through the first and the second dispersive element after coupling to the pulse shaper can be adjusted without any change in an offset between the coupling direction and the exit direction. The first and the second dispersive element are arranged in such a way that the shape of the optical pulse experiences a change as the pulse travels through the pulse shaper.

Abstract: The invention relates to an apparatus for spectroscopically analysing a gas, said apparatus having at least one radiation source (1), at least one detection apparatus (12; 20), at least one sample chamber (13) and a system of optical elements (4; 5; 6; 7; 9; 10; 11; 18; 19) which is intended and set up to direct at least part (3b) of the radiation (3) emitted by the radiation source (1) through the sample chamber (13) onto the detection apparatus (20), wherein the sample chamber (13) is used to hold a gaseous sample which contains the gas to be analysed, and wherein the apparatus is configured in such a manner that the sample can continuously flow through the sample chamber (13), and means (16) are provided for the purpose of determining the pressure and/or the volume and/or the concentration of the sample in the sample chamber (13). The invention also relates to a corresponding method for spectroscopically analysing a gas.