Formation and Detection

Photon, electron, and ion impact on PH3 and electron impact on PD3 were used. 

Photoionization mass spectrometry (PIMS) led to a PHJ appearance potential of 13.40 0.02 eV at 0 K (a measured value of 13.36 0.02 eV was corrected to account for the internal thermal energy of PH3) [1]. 

The formation of PHJ by low-energy electron impact with mass spectrometric detection is dealt with on p. 211 ( Mass Spectrum of PH3 ). Appearance potentials were measured (a way of obtaining the PHJ formation enthalpy) and varied between 13.2 [8, 9] and 14.4 eV [10]. 

Ion cyclotron resonance (ICR) has also been used as a detection method. Single-resonance spectra of PH3 bombarded with 23 eV [16] or 70 eV [17] electrons showed the PHJ ion. It appeared at 18 eV [17]. 

Thermal energy charge transfer reactions with several cations (Ar+, CO , COJ, Kr ) yielding PHJ were observed with the double resonance technique. Product distribution and rate constants (not for Kr+) were measured (see p. 217) [18]. PHJ from the ion-molecule reaction PH3 + PH PHJ + PH2 had been earlier observed by ICR [16]. 

Formation of OF was also observed [3], when F2-N2O mixtures were photolyzed in an N2 or an Ar matrix at 4 K. The OF radical had not been detected previously under these conditions (Ar matrix) [4]. This was attributed to the reactions 0F + F 0F2 and 0F+F2- OF2+F, favored by a large excess of fluorine. The IR detection of OF [4] may also have been prevented by the presence of SiF4 which shows strong absorption in the region of the OF fundamental band [3]. 

OF radicals were also produced and were detected by IR spectroscopy, when OF2 diluted in Ar was co-deposited with a beam of alkali metal atoms (Li, Na, K) or Mg atoms on a Csl window at 15K [5]. 

The production of the radical through direct combination of 0 and F atoms was observed during Hg-arc photolysis of N2 matrices containing F2 and NO2 molecules at 8 K. The OF radical was detected by its IR absorption band [6], see also [7]. 

The radical was first detected mass spectrometrically as the product of O abstraction by atomic F from O3 [8 to 10], see also [11, 12]  

The abstraction of H from HOF by atomic F in a discharge-flow apparatus at 296 to 298 K was measured mass spectrometrically by determining F concentrations. In about 1 Torr of He carrier gas with an initial F atom concentration of -1.5 xIO cm , the reaction 

---

There are various aspects in complex formation and detection, namely ... 

Gall, J G. and Pardue, M. L. (1969) Formation and detection of RNA—DNA hybrid molecules in cytological preparations. Proc. Natl Acad Sci. USA 63, 378-383. 

Carbohydrates are very difficult compounds to analyze using CE because of their inherent structural complexity, frequent lack of a charge and lack of a UV or fluorescent chromophore. They thus require derivatization to facilitate ion formation and detection. 

When in spring 1992 Germar Rudolf sent out the first draft of his Expert Report on the Formation and Detectability of Cyanide Compounds in the Gas Chambers of Auschwitz to a narrow circle of recipients in science and politics, several historians responded with interest. The media, however, received no notice of the existence of the report. Only in spring 1993, when retired Major General Otto Ernst Remer took a later draft of the expert report, provided it with a peppery political preface, and then sent some 1,000 to 2,000 copies to the media, public attorneys, politicians, and scientists, did a certain circle of the Establishment learn of the existence of this report. 

The problems associated with the formation and detection of molecular beams have already been referred to. They are interrelated and have largely determined which reactions have been studied with this technique. The simplest method to form a beam is to collimate the effusive flow occurring from a low-pressure source, conventionally called an oven, although its temperature may be subambient. Unfortunately, this yields low beam intensities, and the velocities in the beam are thermally distributed. As a result, even for the accurate assessment of the incident-beam intensity, a highly sensitive detector is required. Moreover, the relatively low beam temperature requires that the reaction has a small threshold energy so that an appreciable proportion of the scattering is reactive. 

Key properties of noble gases are summarized in Table 1 other properties are in refs. 6 and 11. The formation and detection of M-Ng bonds provide many of the same challenges as for transition metal-alkane bonds. Comparison of spectra and energetics of species such as Cr(CO)5Xe and Cr(CO)s(alkane) points to further similarities in bond enthalpies. Recent reviews tackle complexes of alkanes in detail . Since investigations of alkane complexes are more frequent than those of xenon complexes, we may use these results to anticipate the formation of further M-Ng bonds [e.g., to HMn(CO)4]. 

Getek TA, Korfmacher WA, McRae TA, et al. Utility of solution electrochemistry mass spectrometry for investigating the formation and detection of biologically important conjugates of acetaminophen. / Chromatogr. 1989 474(l) 245-256. 

Because bone marrow is a relatively well-perfused tissue, its exposure to systemically distributed compounds is generally adequate and can be extrapolated from the plasma concentration. Moreover, the high rate of cell proliferation during erythropoeisis in bone marrow facilitates the formation and detection of micronuclei. 

Aromatic amines (AAs) and heterocyclic aromatic amines (HAAs) are ubiquitous environmental and dietary contaminants, many of which are carcinogens. Compounds of both classes contain an exocydic amino group, which is a prerequisite for their genotoxicity (Figure 7.1). In this chapter, the sources of exposure, mechanisms of metabolic activation, formation and detection of DNA adducts, and biological effects of AA-DNA and HAA-DNA adducts are highlighted. 

Grenon, C. Peters, K. Battacharyya, and W. Volk, Formation and detection of sub peUicle defects by exposure to DUV systems illumination, Proc. SPIE 3873, 162 176 (1999) B.J. Grenon, C. Peters, K. Battacharyya, W. Volk, and A. Poock, Reticle surface con taminants and their relationship to sub pellicle particle formation, Proc. SPIE 5256, 1103 1110 (2003). 

---