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Techniques

Supersonic Jet ExpansionSupersonic Jet Ionization

Many of the experiments in this lab take advantage of the convenient properties of supersonic free jets.  Gas is expanded into vacuum through a small (0.03”) orifice. If the orifice is still much larger than the mean free path of the gas, many collisions will occur in the high-density region near...


Cryogenic Electrospray IonizationCryogenic Electrospray Ionization

A significant component of our research program concentrates on structural characterization of transient chemical species invoked to explain solution‑phase reactivity. An approach developed in the Johnson Lab to isolate these species couples electrospray ionization and cryogenic nanomatrix...


Photofragmentation Mass SpectrometryPhotofragmentation Mass Spectrometry

The infrared photofragmentation experiments performed in the Johnson Lab rely on mass spectrometric methods for both the selective interrogation of molecular ions and the acquisition of their infrared spectra. Time-of-flight mass spectrometry (TOF-MS) is used in tandem with both our...


Isomer SelectivityIsomer Selectivity

To address the possibility of multiple isomers in our experiment, we have developed a pump-probe double resonance scheme that utilizes two tunable infrared lasers and either two or three stages of mass selection. First, a pump laser, whose frequency is scanned through the IR range...


Isomer SelectivityLaser Sources

In order to carry out our photofragmentation experiments, we utilize OPO/OPA (LaserVision) lasers that produce the required tunable infrared radiation over the 600-4500 cm-1 range. These systems exploit the nonlinear optical properties of potassium titanyl phosphate (KTP), potassium titanyl...


Fourier Transform ICRFourier Transform Ion Cyclotron Resonance

To study systems with large mass-to-charge ratios or systems that have very complicated isotope patterns we need a spectrometer with the ability to accurately determine masses so we can be sure we are studying the right ion. For this we use a Fourier transform ion cyclotron resonance...


Photoelectron SpectroscopyPhotoelectron Spectroscopy

Utilizing anion photoelectron spectroscopy we are able to quickly determine the electron affinities and measure the vibrational frequencies of neutral molecules. In this technique, the electrons are ejected from a packet of mass-selected anions (A-) by intersecting it with the harmonics of a Nd:YAG laser ...