Selective detection of singlet gerade metastable states of N2.

Metastable N2 molecules produced by electron impact on N2 are detected using a unique solid nitrogen matrix detector. The time-of-flight system is shown to be selectively sensitive to a(1)Πg and (1)Σg (+) or (1)Γg metastable species. The latter species had been identified theoretically previously but was detected experimentally for the first time in the present investigation. Their identification and excitation as a function of electron energy from threshold to 300 eV are presented. Comparison is made with the data obtained by other techniques.

Use of solid N2 surfaces in metastable particle detection.

A novel detector is described in which solid nitrogen at 17 K is used as the most significant element. Metastable particles impinge on this element and immediately transfer their internal energy to the solid nitrogen producing photons, via excimer formation or otherwise, whose wavelength depends on the metastable being detected and the energy transfer process. The performance of the instrument for the detection of atomic oxygen and molecular nitrogen metastables is discussed.

Dissociative excitation and fragmentation of S8 by electron impact.

The vacuum-ultraviolet emission spectrum from 136 nm to 168 nm following the dissociative excitation of a predominantly S(8) target by electron impact at 100 eV incident energy was measured. The relative cross sections for the dominant multiplets at 138.9, 142.9, 147.9, and 166.7 nm are presented. Excitation functions are shown for electron-impact energies from below threshold to 360 eV for the two most prominent emissions at 142.5 nm and 147.4 nm. Five thresholds are clearly apparent in both excitation functions. For the four highest energy channels, the energy separation between the adjacent thresholds is approximately constant and the cross sections reduce regularly as the threshold energies increase. We suggest possible fragmentation pathways of the dissociating S(8) molecule that reproduce the energies of our observed thresholds.

S(1S) production following electron impact on thiophosgene (Cl2CS).

A special xenon matrix detector has been used to study the production of S(1S) following controlled electron impact on thiophosgene (Cl2CS) targets over an electron energy range from threshold to 400 eV. Time-of-flight spectroscopy has been used to measure S(1S) fragment kinetic energies. Fragments with energies in excess of 1 eV have been observed. The absolute cross section for S(1S) production reaches a maximum of [1.05+/-0.35] x 10(-18) cm2 at approximately 125 eV impact energy. Two different fragmentation processes, involving triplet and singlet excited states of the parent Cl2CS molecule, have been identified.

POLAR: a menu driven computerized analysis of fluorescence polarization data.

While fluorescence polarization is a powerful tool for the measurement of ligand-receptor (e.g. antigen-antibody) interactions, its application in routine clinical chemistry and immunochemistry has been limited because collection of data was error prone, and because analysis of data previously required tedious and imprecise manual graphical methods. We present the series of linear and curvilinear regressions required to calculate parameters (p', Q', pf, Qf, Pb, Qb, Fb max, a and Ko) and their corresponding standard errors. The values of a and Ko are comparable to those obtained by the method of finding the minimal the sum of squares. A menu operated computer program that uses these regressions, simplifies the collection, analysis and presentation of fluorescence polarization data. A simple spread sheet system permits the insertion, deletion or modification of data. The results are presented in graphical and tabular form, either on a monitor, a printer or an X-Y plotter. The system has its own graphical routines.

Sensitivity response of channel electron multipliers and channel plates to the polarization of VUV radiation.

It is demonstrated that both channel electron multipliers and channel plates may display pronounced polarization sensitivity when VUV radiation is being detected. Photon angle of incidence is demonstrated to be an important parameter for channel plates.