Essentially, the experiment consists of a small amount of sample material being placed on a platinum filament which is then inserted into an IR cell. The cell can be evacuated and filled with gas at a pressure of choice.  The filament is then heated to a desired temperature causing  flash pyrolysis of the material.  While the sample is being heated and is decomposing,  the decomposition products are detected by the rapid-scan FTIR spectrometer.  These products give not only decomposition mechanism information, but sometimes kinetic data.  This provides information which has been traditionally elusive; namely, the initial products of decomposition of fast burning and energetic materials such as rocket propellant ingredients and explosives.
 
 

Application of T-Jump Experiment:

        In the field of combustion, the chemistry in the thin zone at a burning surface has long defied experimental description because a complex heterophase, nonequilibrium reaction network exists over a very short short length and a steep temperature gradient.  We develop new techniques to stimulate the burning surface of solid materials, and outline the reaction networks for the first time.  Various methods are used for fast, controlled heating of small amounts of material coupled with real-time detection of the chemistry by rapid-scan FTIR spectroscopy.  The choice of materials is based on the practical importance of the decomposition mechanisms and products.  They include polymers, gas generators, explosives, and rocket propellants.   Projects within the group are tailored to each student's interest in technique design, synthesis of model compounds, fast decomposition studies, and data analysis techniques.
 

    A special IR cell (as shown below) must be employed in order to perform the T-jump experiment in an oxygen free environment at a desired pressure.  The "Brill Cell", as it has come to be called, satisfies these requirements.  It is essentially an aluminum pressure cylinder (A) with IR transparent windows (Zinc Selenide) on either end.   Phenolic curtains (B) are used to maintain an IR transparent gas purge between the windows and the cell compartment sides of the IR spectrometer (in this case a Nicolet Model 800 bench, C).   Three ports are fitted to the cell.  One port (D) serves as both the control gas inlet and the pressure gauge (E) port.  Another serves as a gas bleed-off (F).  The last is the inlet into which the probe containing the fillament and sample is inserted (G).  The stage onto which the cell is placed is designed to direct the beam path directly above the probe's filament.
 
 

        The pyroprobes we use (as shown below) are made by CDS Analytical (.  They are essentially a coaxial bar (H) with the inside conductor and insulation recesed about 2 inches and a "top" and "bottom" window cut from the outside conductor.  This allows a Platinum filament (I) to be attached to the inside conductor on one end and the outside conductor at the tip, thus closing the circut.  The other end contains leads (J) which are connected to the power source inside an insulating handle.  The probe is fitted with a gas sealing ferrul (K) which makes the pressure seal with the probe port in the Brill Cell and a nut (L) used to tighten the probe into place.  A plastic fitting (M) further to the rear of the probe holds the probe tightly in the abovementioned handle and prevents it from turning freely.   Before the experiment a very small amount of material is placed on the filament.   The probe is then carefully inserted into the Brill Cell and the experiment conducted.