Photoionization Mass Spectroscopy

CRF researchers have pioneered the use of multiplexed mass spectrometry (simultaneously detecting many masses) in combination with photoionization by tunable synchrotron radiation—which provides isomeric specificity through the photoionization spectroscopy—as a powerful tool for investigating elementary reaction kinetics and the chemistry of low-pressure flames. This method provides multidimensional data sets as a function of mass, photon energy, and the physical dimension of the system, e.g., distance from the burner or time after reaction initiation, as depicted in Figure 1.

Figure 1: The data can be quantitatively correlated and integrated along any of the dimensions to compare to traditional measurements such as time or distance profiles of individual chemical species or photoionization spectra for isomeric analysis.

The technique has two substantial advantages for analysis of complex chemical systems such as flames or multiple-channel chemical reactions. First, the simultaneous detection of multiple species gives a time advantage and also “automatically” detects even unexpected chemical intermediates. Second, and perhaps more valuably, the easily tunable photon energy allows researcher to determine isomeric composition through the photoionization spectrum. This can be made quantitative through comparison to reference spectra, as shown in Figure 2, where the isomers at mass @%@% are determined in two low-pressure flames.

Figure 2