The height of a signal is proportional to the amount of that ion present in the spectrum and the m/z of the ion is basically the mass of that ion (if it is singly charged). From close measurement of the exact mass of the ion, or the difference in m/z between ions, then their molecular formula can be determined. Because n may be a very high number, it is not possible to get intact molecular ions of individual polymer chains into the gas phase using TOF-SIMS. Instead, we observe a series of fragment ions that can provide information about the polymer structure. In this case, a peaked representative of the polymer oligomeric unit can be seen at m/z 193: (C₁₀H­O₄)H⁺. Various other peaks are observed in the lower mass range below m/z 193 that are structurally significant and are related to the chemical structure of the sample under analysis. . Careful analysis of the mass and identity of these peaks can enable the polymer structure to be determined, or at least estimated, for complete unknowns.  For example, in the case of PET, masses 104, C₇H₄O⁺ and 149, C₈H₅O₃⁺  are detected as prominent fragment ions in the positive ion spectrum, and masses 121, C₇H₅O₂^– and 165, C₈H₄O₄– are detected in the negative ion spectrum.. For unknown samples, it is necessary to identify as many of the peaks in the spectra obtained as possible, and from these identified species, piece together the potential identity of the material under investigation.