Argon ions

Table 7.40 Principal Argon-Ion Laser Plasma Lines 7.88...

With continuous lasers (for example an argon ion laser), the energy delivered is usually much less than from pulsed ones, and the focusing is not so acute. Thus, the irradiated area of the sample is more like 10 cm rather than 10" cm, and the energy input is much less, about 100 kW/cm rather than the 100,000 kW/cm described earlier. 

For mass spectrometric purposes, the plasma is normally created in argon, a monatomic gas. The plasma then consists of electrons, positive argon ions, and neutral argon atoms. 

Figure 5.17 shows the rotational Raman spectrum of N2 obtained with 476.5 nm radiation from an argon ion laser. From this spectrum a very accurate value for Bq of 1.857 672 0.000 027 cm has been obtained from which a value for the bond length tq of 1.099 985 0.000 010 A results. Such accuracy is typical of high-resolution rotational Raman spectroscopy. 

A further advantage, compared with the alexandrite laser, apart from a wider tuning range, is that it can operate in the CW as well as in the pulsed mode. In the CW mode the Ti -sapphire laser may be pumped by a CW argon ion laser (see Section 9.2.6) and is capable of producing an output power of 5 W. In the pulsed mode pumping is usually achieved by a pulsed Nd YAG laser (see Section 9.2.3) and a pulse energy of 100 mJ may be achieved. 

CW dye lasers are usually pumped wifh an argon ion laser, up to abouf f W of continuous dye laser power being produced, compared wifh abouf f MW peak power which may be produced in a pulsed dye laser. 

Argonaut Argon difluoride Argon fluoride Argon-helium Argon ion lasers Argon-oxygen... 

Ion implantation (qv) direcdy inserts nitrogen into metal surfaces. A carefully poHshed and cleaned metal surface at room temperature in a vacuum (-- 0.133 mPa (l-) m Hg)) can be directly implanted with 80-keV nitrogen ions (10) (see Metal surface treatments, case hardening). In an alternative synthesis, argon ions (Ar ) of 8 keV can be used to ionize gas-phase nitrogen to obtain the same results (17). 

Fig. 8. Calculated sputtering yield of several materials bombarded with argon ions at various energy levels. The materials Hsted parenthetically also have...

Current practice in depth profiling is to use positively charged argon ions at energies between 0.5 and 10 keV, focused into a beam of 2-5-p.m diameter, which is then ras-... 

When a heavy energetic particle such as an argon ion (typically 1 to 15 keV) hits a surface, it will not be stopped short by the first layer of atoms but continues into the surface until it comes to a halt as a result of energy lost in atomic and electronic scat-... 

The original TOP design [3.9] used pulsed beams of argon ions, but commercial development of the LMIS has significantly extended the capabilities of the TOP system. 

Figure 6.6. The surface of a liii crystal following bombardment with 5 kcV argon ions, imaged in a. scanning electron microscope (Stewart and Thompson 1969).

UHV is necessary but not sufficient to ensure an uncontaminated surface. Certainly, the surface will not be contaminated by atoms arriving from the vacuum space, but such contamination as it had before the vacuum was formed has to be removed by bombardment with argon ions. This damages the surface structurally, and that has to be healed by in situ heat treatment. That, however, allows dissolved impurities to diffuse to the surface and cause contamination from below. This problem has to be dealt with by many cycles of bombardment and annealing, until the internal contaminants are exhausted. This is a convincing example of Murphy s Law in action one of the many corollaries of the Law is that new systems generate new problems . 

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