Vapor signature

Figure 7. Simultaneously monitoring vapor signatures of 1000 sensors for 2,4-DNT, 1,3-DNB, and TNT vapor strips at 8% saturated vapor levels. The (noisy) responses for 250 individual sensors are compared to the averaged response profile for 1000 individual sensors. Reprinted with permission from ref. 12a. Copyright 2000 American Chemical Society.

At the time of the studies described, and up to the present, a vapor sensing system with sensitivity adequate to routinely discover the vapor signature from buried landmines has not been fielded in quantity. Therefore, it is necessary to estimate the concentrations that may be expected, so that system developers may form realistic design goals. Jenkins and his colleagues estimated the air concentrations, for one kind of soil and two types of mines, as shown in Table 4.5 [8], The quantity Ks/a is equivalent to the K previously defined. It was calculated as the ratio of soil residue to vapor concentration in their experimental samples. 

Vapor signatures become stronger or weaker at some times, depending on the moisture and temperature cycles. 

There will be no vapor signature when the surface temperature falls below freezing. 

We may reasonably expect IEDs to be disguised. Penetrating the disguise may frustrate the efforts of their user. Some objects may be hidden by debris. Expected vapor signatures from these items required search in air. Many ordnance items are used in water others are disposed of there. Search for traces of explosives from them may be expected to be somewhat different. 

J. Pennington. Progress on Determining the Vapor Signature of a Buried Landmine , Proc. SPIE, Detection and Remediation Technologies for Mines and Minelike Targets... 

DMMP), dimethyl phosphonate (DMHP) or diisopropyl methylphosphonate (DIMP) are commonly used as simulants. For nitroaromatic detection, 2,4-dinitrotoluene (2,4-DNT) is a commonly used simulant, although many TNT-based explosives often have a significant component of 2,4-DNT in the vapor signature. 

Water is an important molecule in circumsteUar material as weU as in the interstellar medium. There are known strong far infrared transitions. Therefore it can act as a coolant in shocks and circumsteUar outflows. The cm-wavelength water vapor signatures on the other hand indicate star forming regions and cool stars. 

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