Abstract: Molecular rotational resonance (MRR) spectroscopy can be used to characterize neutral, gas-phase molecules with very fine spectral resolution. Typically, the analyte molecules are placed in solution, which is heated initially to evaporate the solvent, then heated more to volatilize the analyte. Unfortunately, this approach does not always work well for analytes with low volatilities or susceptibility to thermal degradation. These analytes can be volatilized instead using laser-induced acoustic desorption (LIAD), flash vaporization, or nebulization. In LIAD, the analyte is dried onto a metal foil, which is illuminated by a laser. The laser beam generates an acoustic wave in the metal foil that shakes off the analyte. In flash vaporization, a small amount of liquid analyte drips onto a very hot surface, where it vaporizes too quickly to degrade. And in nebulization, a nebulizer pumps a fine spray of analyte into a heated transfer tube, where the solvent evaporates.

Abstract: The capabilities of a gas or liquid chromatography-molecular rotational resonance (GC/LC-MRR) instrument exceed those of high-resolution mass spectrometry and nuclear magnetic resonance in terms of selectivity, resolution, and compound identification. MRR detection provides high specificity for selective gas- or liquid-phase separations, including the ability to resolve co-eluting peaks and isomeric compounds without any loss of specificity or accuracy. MRR can perform both qualitative identification and absolute quantification of analyte components separated by GC or LC without a reference standard. GC-MRR is ideal for compound-specific isotope analysis (CSIA) and can identify enantiomers and enantiomeric excess. GC-MRR measurements are especially useful for studying biosynthetic/degradation and geochemical isotopic compounds.

Abstract: Methods and apparatuses for direct multiplication Fourier transform millimeter wave spectroscopy are disclosed herein. A sample method includes generating at least one pulse of microwave electromagnetic energy. The sample method also includes frequency-multiplying the pulse(s) to generate at least one frequency-multiplied pulse and filtering at least one spurious harmonic of the frequency-multiplied pulse to generate at least one filtered pulse. The spurious harmonic is generated by frequency-multiplying the pulse. The method also includes exciting a sample using the filtered pulse. The method further includes detecting an emission from the sample. The emission is elicited at least in part by the filtered pulse.

Abstract: Methods and apparatuses for direct multiplication Fourier transform millimeter wave spectroscopy are disclosed herein. A sample method includes generating at least one pulse of microwave electromagnetic energy. The sample method also includes frequency-multiplying the pulse(s) to generate at least one frequency-multiplied pulse and filtering at least one spurious harmonic of the frequency-multiplied pulse to generate at least one filtered pulse. The spurious harmonic is generated by frequency-multiplying the pulse. The method also includes exciting a sample using the filtered pulse. The method further includes detecting an emission from the sample. The emission is elicited at least in part by the filtered pulse.

Abstract: Apparatus and techniques for broadband Fourier transform spectroscopy can include frequency hopping spread-spectrum spectroscopy approaches. For example, an excitation source power can be spread over a specified frequency bandwidth, such as by applying a sequence of short, transform-limited pulses to a sample. Each pulse can include a specified carrier frequency, and a corresponding bandwidth of the individual pulse can be determined by a frequency domain representation when Fourier transformed. A series of short excitation pulses can be used to create an excitation sequence, such as to deliver a specified or desired amount of power to the sample, such as by having the excitation source enabled for a time comparable to a free induction decay (FID) dephasing time.