data distribution function three-dimensional mass spectrum 3D mass spectrum 3D mass spectra three-dimensional mass spectrum three dimensional mass spectrum three-dimensional mass spectra three dimensional mass spectra 3-dimensional mass spectra 3-dimensional mass spectrum A three-dimensional mass spectrum is a data distribution function of counts versus m/z and versus time obtained by counting the ions produced by a sample as a function of their mass-to-charge ratio and as a function of time. [Allotrope]