The present invention provides an apparatus and method for use with a mass spectrometer. The multimode ionization source of the present invention provides one or more atmospheric pressure ionization sources (e.g., electrospray, atmospheric pressure chemical ionization and/or atmospheric pressure photoionization) for ionizing molecules. A method of producing ions using the multimode ionization source is also disclosed. The apparatus and method provide the advantages of the combined ion sources without the inherent disadvantages of the individual sources. In an embodiment, the multimode ionization source includes an infrared emitter enclosed in an inner chamber for drying a charged aerosol. ESI/APCI multimode sources may include a corona needle shield and/or an auxiliary electrode.