have the form of a double funnel i e first narrowing and then widening out again in these openings the jets of sheath gas are guided to surround and focus the spray jets each spray jet consists of ions and highly charged very fine droplets which repel each other and try to drive each other out of the spray jet in a radial direction the funnel causes the sheath gas to closely envelop each individual spray jet this means that heavy ions and droplets of the spray jet are prevented by their low mobility from penetrating through the sheath gas and discharging on the inner surfaces of the openings although the attracting voltage electrode attracts the charges of the droplets and the ions in addition to their mutual space charge repulsion the drying process of the droplets is very complicated the increasing charge density on the surface of the shrinking droplets repeatedly causes the droplets to become constricted and divide but also directly expulses light ions mainly charged water clusters the droplets cool due to the loss of heat of vaporization they can even freeze in the limiting case the sheath gas should therefore preferably be heated in order to accelerate the drying process of the droplets the temperature here must be chosen so that on the one hand the droplets dry rapidly but on the other hand the analyte ions are not destroyed and consideration must be given to the fact that the drying process cools the analyte ions and thus protects them it is quite possible to use temperatures of over one hundred degrees celsius highly focused and hot jets of sheath gas also support the.