Secondary yields

The average number of emitted particles X per incident primary ion is given by the secondary yield Y (X ) ... 

The secondary ion yield depends both on the energy and the nature of the primary ions. It has been demonstrated that the use of clusters instead of monoatomic ions improves the secondary yield. Classical primary ions, like Ga+ and Cs+, are increasingly replaced by Au3+, Bi3+ or C60+ which has permitted great progress in organic ToF-SIMS studies [Kollmer 2004, Touboul et al. 2004, Winograd 2005]. 

In the Simple model, taking the primary yield as px and the secondary yield as piz, the primary abundance is... 

An interesting alternative technique was discussed by Harris, et al. (11) who made a contactless measurement. A toroidal specimen is formed of the superconductor and is used as the tertiary winding of a small ferrite transformer. Signals from the secondary yield the resistivity in the normal state. Measurements were made at a 20 kHz frequency. 

As only those alcohols which are primary yield aldehydes so also only those which are secondary yield ketones. The relation in composition between the secondary propyl alcohol and acetone is the same as between ethyl alcohol and acetaldehyde. What then is the constitution of ketones and why do secondary alcohols not oxidize to aldehydes but to ketones ... 

Benzyl alcohol or phenyl methyl alcohol given above can, of course, exist only as a primary alcohol there being only one carbon group in the side chain. Like the aliphatic alcohols, the primary yield aldehydes and then acids on oxidation, the secondary yield ketones and the tertiary break down. 

An additional option for generation of fragments from glycan precursors is dissociation with photons, usually generated from a CO2 laser at 10.6 pm (33). Irradiation of the trapped ions results in multiphoton absorption and dissociation of all species, both primary and secondary, yielding spectra that are rich in fragment ions (34). 

A fission product is hence normally produced in two ways Directly from the fissioning nucleus and indirectly by the P decay of a precursor. Correspondingly, one can distinguish between independent (primary) and secondary yields. The sum of primary and secondary yields is called cumulative yield. The cumulative yield of the last chain member is normally identical to the chain yield. Fractional (independent, cumulative, etc.) yields show what fraction of the total chain yield comes from a particular formation path. 

In principle, the magnitude of the secondary yield at beam energies E > Ej is a function of the chemistiy of the surface since the secondary yield varies slowly with atomic number. However, in most current SEMs the vacuum is sufficiently poor that the surface is always covered with many monolayers of contamination, such as hydrocarbons, deposited from the pumping system. Because the secondary electrons can escape only when produced within a few nanometers of the surface, changes due to the surface chemistry are therefore usually masked. 

After the primary step in a photochemical reaction, the secondary processes may be quite complicated, e.g. when atoms and free radicals are fcrnied. Consequently the quantum yield, i.e. the number of molecules which are caused to react for a single quantum of light absorbed, is only exceptionally equal to exactly unity. E.g. the quantum yield of the decomposition of methyl iodide by u.v. light is only about 10" because some of the free radicals formed re-combine. The quantum yield of the reaction of H2 -f- CI2 is 10 to 10 (and the mixture may explode) because this is a chain reaction. 

An optically active, secondary terpene alcohol. ( —)-Piperilol is found in various eucalyptus oils and (-l-) piperitol in the oil from a species of Andropogon. A somewhat viscous oil of pleasant smell. It yields piperitone on oxidation with chromic acid. 

With the exception of the scanning probe microscopies, most surface analysis teclmiques involve scattering of one type or another, as illustrated in figure A1.7.11. A particle is incident onto a surface, and its interaction with the surface either causes a change to the particles energy and/or trajectory, or the interaction induces the emission of a secondary particle(s). The particles that interact with the surface can be electrons, ions, photons or even heat. An analysis of the mass, energy and/or trajectory of the emitted particles, or the dependence of the emitted particle yield on a property of the incident particles, is used to infer infomiation about the surface. Although these probes are indirect, they do provide reliable infomiation about the surface composition and structure. 

P -f lOROH -f 5Br, — 2H3PO, -f lORBr -f 2H,0 The reaction is of general application with primary alcohols (n propyl to n hexadecyl) the yields are over 90 per cent, of the theoretical, but with secondary alcohols the yields are 50-80 per cent. in the latter case a small quantity of high boiling point by-product is also formed which can, however, be readily removed by fractional distillation. The reaction is conveniently carried out in a special all glass apparatus. 

The reaction is of general application the yields of primary alcohols approach the theoretical values, and for secondary alcohols are 85-95 per cent. The process is best carried out with the aid of a special apparatus. 

Phenylthioureas. Primary and secondary amines react with phenyl isothiocyanate to yield phenylthioureas ... 

Secondary amines upon treatment with nitrous acid yield nitrosamiues, which are stable, neutral yellow liquids (or low melting point solids), for example ... 

Certain primary amines yield disulphonyl derivatives, which are insoluble in alkali and therefore may be confused with the monosulphonyl derivatives of secondary amines. 

Derivatives with 3-nitrophthalic anhydride. 3-Nitrophthalic anhydride reacts with primary and secondary amines to yield nitro-phthalamic acids it does not react with tertiary amines. The phthalamic acid derived from a primary amine undergoes dehydration when heated to 145° to give a neutral A -substituted 3-nitrophthalimide. The phthalamic acid from a secondary amine is stable to heat and is, of course, soluble in alkali. The reagent therefore provides a method for distinguishing and separating a mixture of primary and secondary amines. 

Formyl derivatives. Formic acid condenses with primary and secondary amines to yield formyl derivatives ... 

Tertiary amines capable of eliminating a secondary amine to form a conjugated system can react with hydrogen cyanide to form y-keto nitriles by amine replacement. Thus (I) yields p-benzoylpropionitrile (IV) ... 

In the above reaction one molecular proportion of sodium ethoxide is employed this is Michael s original method for conducting the reaction, which is reversible and particularly so under these conditions, and in certain circumstances may lead to apparently abnormal results. With smaller amounts of sodium alkoxide (1/5 mol or so the so-called catal3rtic method) or in the presence of secondary amines, the equilibrium is usually more on the side of the adduct, and good yields of adducts are frequently obtained. An example of the Michael addition of the latter type is to be found in the formation of ethyl propane-1 1 3 3 tetracarboxylate (II) from formaldehyde and ethyl malonate in the presence of diethylamine. Ethyl methylene-malonate (I) is formed intermediately by the simple Knoevenagel reaction and this Is followed by the Michael addition. Acid hydrolysis of (II) gives glutaric acid (III). 

Acetyl chloride reacts vigorously with primary and secondary alcohols to yield esters it also reacts readily with any water present to form acetic acid ... 

The reason for this is that reaction (i) is usually much slower than (ii) and (iii) so that the main reaction appears to be (Iv) (compare the preparation of tertiary butyl chloride from tertiary butyl alcohol and concentrated hydrochloric acid, Section 111,33). If the reaction is carried out in the presence of P3rridine, the latter combines with the hydrogen chloride as it is formed, thus preventing reactions (ii) and (iii), and a good yield of the ester is generally obtained. The differentiation between primary, secondary and tertiary alcohols with the aid of the Lucas reagent is described in Section III,27,(vii). 

Benzenesulphonyl chloride reacts with primary and secondary, but not with tertiary, amines to yield substituted sulphonamides (for full discussion, see Section IV,100,3). The substituted sulphonamide formed from a primary amine dissolves in the alkaline medium, whilst that produced from a secondary amine is insoluble in alkali tertiary amines do not react. Upon acidifying the solution produced with a primary amine, the substituted sulphonamide is precipitated. The reactions form the basis of the Hinsberg procedure for the separation of amines see Section IV,100,(viii) for details. Feebly basic amines, such as o-nitroaniline, react slowly in the presence of allcali in such cases it is best to carry out the reaction in pyridine solution see Section IV,100,3. ... 

Some reference to the use of nitrous acid merits mention here. Primary aromatic amines yield diazonium compounds, which may be coupled with phenols to yield highly-coloured azo dyes (see Section IV,100,(iii)). Secondary aromatic amines afford nitroso compounds, which give Liebermann a nitroso reaction Section IV,100,(v). Tertiary aromatic amines, of the type of dimethylaniline, yield p-nitroso derivatives see Section IV,100,(vii). ... 

---