Metastable helium reactions

The detector has two sections the upper section consisting of a tube 1.6 mm ID. (where the discharge takes place) and the lower section, 3 mm I.D. (where reaction with metastable helium atoms and photons... 

The photons and metastable helium atoms enter the reaction zone where they meet the eluent from the capillary column. The solute molecules are ionized and the electrons produced are collected at the lower electrode and measured by an appropriate high impedance amplifier. The distance between the collecting electrodes is about 1.5 mm. The helium must be 99.9995 pure. The base current ranges from... 

At this point the identity of X remains unspecified.. X could be, for example, the metastable 23S helium atom, in which case X represents a ground state He atom plus an electron. Alternatively X could be the He2+ molecule-ion, and X would then represent two ground state helium atoms. For simplicity we assume that under any one set of conditions only one excited helium species is dominant, although we can expect several processes occurring simultaneously. The natural lifetime of N2+ or 02+ is short compared with the time scale of the experiment, and thus the emission intensity is proportional to the rate of Reaction 1. If the concentration of nitrogen is uniform and constant along the tube, which should be the case after some distance of travel, the intensity... 

So far we have not considered the identity of the excited helium species X. Collins and Robertson (3) have shown that the upper state of N2+ giving rise to the blue emission is populated by reaction of N2 with both metastable 23S He and He2+. Similarly, they have shown that 23S He reacts with 02 to populate the upper state of both band systems of 02+, while He2+ reacts with 02 to populate only the upper state of the 5586 A. system. 

The meta-elements of Crookes anticipated the idea of isotopes. The most readily available sources of separated stable isotopes are lead 206 from uranium minerals and lead 208 from thorium minerals, and it is interesting enough that before 1910 several successful chemical separations of radioactive isotopes of the same element were reported, involving both thorium 230 (ionium) and lead 210 (radium D). In otir opinion, this can only be due to kinetically metastable chemical nonequivalency in the mixture, for instance, due to colloidal or oligomeric complexes. The valuable conclusion of this story is that the chemical similarity of trivalent rare earths is so striking that doubts have been expressed whether they deserved more than one place in the Periodic Table, a situation isotopes later had to accept. Such a doubt has never been expressed for any other elements, not even for a pair of elements like vanadium and chromium, which were confused at the time of their discovery (7). Nevertheless, studies based on the possibility of metaelements continued rather late for instance, Debierne attempted to separate neo-radium from conventional radium 226 and to perform nuclear reactions on charcoal cooled with liquid helium (77). 

The influence of moisture in an IMS measurement begins with the formation and composition of reactant ions available in the reaction region of the drift tube. While the formation of hydrated protons can be assumed when moisture is 1 ppm and above, at levels of moisture of 100 ppb and below, the lifetime of ions such as H2O, N4+, and N2+ may be sufficient for reactions with analyte." At practical extreme moisture levels, 10 ppb and below, metastable ions may exist in helium." Consequently, a continuum of ion populations with moisture can be anticipated in both the reactant ion, and the associated reactions depend on moisture. 

Reactions of helium metastables, e.g. He(2 Sq) with an excitation energy of 20.6 eV, will nearly always involve ionization. For example... 

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