KrF laser radiation

Figure 1. Transient IR spectra following photolysis of Fe(C0>5 with XeF and KrF laser radiation. Traces are taken -1 nsec after photolysis. In addition to Fe(C0>5 (30 mtorr for KrF, 200 mtorr for XeF) the photolysis cell contained 5 torr Ar. The symbols are defined in the text.

Laser-induced decomposition of mixtures of polychlorinated biphenyls in the liquid phase has been investigated, employing radiation from three different excimer lasers (XeCl at 308 nm, KrF at 248 nm and ArF at 193 nm)475. The mixtures can be quantitatively and efficiently destroyed by means of UV radiation at 248 nm. A single-photon dissociation process, which leads to both HC1 elimination and biphenyl bond rupture, is induced by the KrF laser radiation. 

Temperature programmed desorption experiments have been used to examine the photochemical properties of MoCCO) adsorbed on Si(lOO). At 150 K, KrF laser radiation (248 run) partially decomposes the adsorbed Mo(CO) releasing gas-phase CO. MoL, (HL.=monothiodibenzoylmethaune) has been synthesised by UV induced oxidative decarbonylation of Mo(CO) in the presence of HL in THF. Similarly, M(CO), Sn[N(SiMe,) and... 

Fig. 10.6 Characteristic mass spectra of ions formed upon irradiation of crystalline powders of (a) anthracene and (b) adenine by KrF laser radiation. (From Antonov et al. 1980a, 1981ft.)...

Draw a diagram similar to that in Figure 9.21 to illustrate the stimulated Raman effect in FI2. Fligh-pressure FI2 is used to Raman shift radiation from a KrF laser. Calculate the two wavelengths of the shifted radiation which are closest to that of the KrF laser. 

Finally, it is interesting to note that under exposure to krypton fluoride (KrF) excimer laser radiation supphed in several shots of 350 mJ/cm the S-layer is not ablated but car-... 

Most resists are designed for exposure at wavelengths longer than the 248.4 nm radiation provided by a KrF laser source. Wolf and coworkers O) have found that the choice of a positive resist for use at thTis wavelength is limited. They evaluated a number of positive resists. Only Microposit 2415, and its newer analog, Microposit 2400-17, were compatible with the anticipated exposure time of 0.5 to 1.0 seconds for resist sensitivity of 100 to 200 mj/cm needed with the new exposure tool developed by Pol and coworkers. (O The resist consists of three components a resin, a photoactive compound or PAG (which acts as a dissolution inhibitor), and a solvent. Upon exposure, the PAC is destroyed, and this allows the resist film to dissolve in the aqueous basic developer. 

Frequency tripling of KrF laser output in Xe results in radiation near 83 nm, tunable over a region of 0.5 nm, and this has been used to measure absorption line profiles in the system in H2, and the corresponding B" - X... 

UV light with a wavelength of 254 nm can be generated with a mercury vapom lamp and the appropriate filters. U V radiation with a wavelength of 350 nm is obtained with an yttrium-aluminium-garnet (YAG) laser. Optional is as well the irradiation with a KrF laser (248 nm), or a nitrogen laser (337 nm). 

In the past fifth harmonic generation has been investigated with powerful fixed frequency solid state (Nd-YAG or Nd-Glass) and gas (XeCl, KrF) lasers . In one of these experiments input powers of more than 300 MW (mode-locked Nd-YAG fourth harmonic, X=266.1 nm) provide, for example, conversion efficiencies of 10 to 10 . Since the pulse power of most dye laser systems is lower by one or two orders of magnitude nonresonant fifth-order frequency mixing of this radiation would produce intensities below a useful level. 

Fifth-harmonic conversion has been used to generate radiation at wavelengths as short as 38.6 nm using radiation from an ArF laser at 193 nm, seventh-harmonic conversion has been used to generate radiation at wavelengths as short as 35.5 nm with radiation from a KrF laser, and ninth-harmonic conversion has been used to generate radiation at... 

Finally, it is interesting to note that under exposure to krypton fluoride (KrF) excimer laser radiation supplied in several shots of 350 mJ/cm the S-layer is not ablated but carbonized, in the exposed areas [109,156]. This result is already used for high resolution patterning of polymeric resists (Figure 18). S-layers that have been formed on top of a spin-coated polymeric resist (on a silicon wafer) have been first patterned by ArF radiation and subsequently served as a mask for a blank exposure of the resist by irradiation with KrF-pulses. This two-step process was possible because S-layers are less sensitive to KrF radiation than polymeric resists. The thinness of the S-layer mask causes very steep side walls in the developed polymeric resist. 

For any true microspectrochemical analysis a microscope and a dispersing instrument are needed. An essential feature of a laser microscope is that the objectives for both the observation of the specimen and for focusing the laser radiation must be suitable for ablation, vaporisation, and excitation of the material. The defining attribute of LMMS is the use of a high power pulsed UV laser ultimately focused down to the dil action-limited spot (0.5 ixm at 266 nm) to vaporise, atomise, and ionise a microvolume of a solid specimen in a one-step procedure. Laser microprobe mass analysers are typically equipped with Nd YAG lasers (1064 and 266 nm 5-15 ns pulses) or excimer lasers (XeF, 351 nm XeCl, 308 nm KrF, 248 nm with about 7-30 nm pulses). Power densities of up to 10 Wcm 2 are quite common organic compounds require attenuation to about 10 -10 W cm . By adjusting the laser power, desorption and ionisation can, to some extent, be selected over ablation and dissociation in the microplasma. 

---