Wavelength laser spectrum

The most notable feature of these intrazeolite photooxygenations (Fig. 30) is that the oxygen CT band experiences a dramatic bathochromic shift in comparison to solution. This was detected initially by recording the product growth as a function of irradiation wavelength (laser reaction excitation spectrum)98,110 and was later verified by direct observation using diffuse reflectance UV-Vis spectroscopy.111 For example, 2,3-dimethyl-2-butene CT-absorbance is shifted to lower energy by more than 300 nm... 

Figure 2. Luminescence spectra of CeoFWS excited by different laser wavelengths. Raman spectrum of water is subtracted.

Fig. 2.4. a TOF mass spectra are shown for 1,3-cyclohexadiene (1,3-CHD) and b 1,4-cyclohexadiene (1,4-CHD) at 0.8 pm with a 120-fs pulse width at an irradiation intensity of 0.6 x 1014Wcm 2. The molecular ions are indicated by M+ and the candidate for the doubly charged molecular ions is indicated by M2+. The excitation laser spectrum is indicated in the inserted Figs. 1,3-CHD+ is not in resonance with the laser wavelength, which resulted in a high yield of molecular ions, whereas 1,4-CHD+ is resonant and gave many fragments... 

Common Laser Wavelengths. Lasers can produce radiation in the ultraviolet, visible, and infrared regions of the spectrum. Table 6-B lists several common laser lines and the medium used to produce the laser. 

Figure 5.14 Transient spectrum of singlet phenylnitrene produced upon LFP of phenyl azide. Spectrum 1 was recorded 2 ns after laser pulse (266 nm, 35 ps) at 233 K. Long-wavelength band (spectrum 2) was recorded with an optical multichanal analyzer at 150 K (with a 100-ns window immediately after the laser pulse, 249 nm, 12 ns). The computed positions and oscillator strengths (f, right-hand axes) of the absorption bands are depicted as solid vertical lines. For very small oscillator strengths a value multiplied by 10 is presented (f x 10).

Table 1 shows the refractive indices for several materials. The variation of refractive index as a function of electromagnetic radiation wavelength (dispersion spectrum) provides simultaneous information about the polarizibility and absorption properties of the sample. The rapid development of modern optical and imaging technologies such as lasers and photodiode arrays creates opportunities for application of refractometry to small analytical systems and multidimensional monitoring. 

Wallndfer et al. [963] investigated various anellated and alkylated polythiophenes [(polyisothianaphthene (PITN), polyison-aphthothiophene (PINT), poly(3-octylthiophene) (POT)] prepared by electropolymerization with resonance Raman spectroscopy at various laser wavelengths. " The spectrum of POT is dominated by a strong luminescence (which is related to some of the possible appUcations of this material). The main peak is around 1460 cm ... 

Andrews [9] and others [10] have listed the emission lines of the most commonly available discrete-wavelength lasers (such as ruby, Nd YAG, Er YAG, excimer lasers) over the range 100 nm-10 /u.m. Molecular lasers (HF, CO, CO2, NO) can be tuned to a large number of closely spaced but discrete wavelengths. Continuously tuneable lasers comprise some metal ion vibronic lasers (e.g. alexandrite and Ti sapphire [11]), some diode and excimer lasers, dye and free-electron lasers. Tuneable sources of coherent radiation span the electromagnetic spectrum from 300 nm to 1 mm, with limited tune-ability down to about 200 nm. Wavelength coverages of tuneable lasers have been reported [8]. In operation lasers can be either pulsed (e.g. various metal ion tuneable vibronic lasers, excimer and dye lasers, metal vapour) or continuous wave (major types atomic and ionic gas lasers, dye and solid-state lasers). Most lasers with spectral output in the UV are bulky and expensive devices (especially sub 200 nm) and operate in the pulsed mode. On the contrary, many visible lasers are available which are compact, require low maintenance expenses and operate in continuous-wave (CW) mode. 

Figure 10.2 shows a typical experimental arrangement for sub-Doppler spectroscopy in molecular beams. The photomultiplier PM 1 monitors the total fluorescence Ip- (XL) as a function of the laser wavelength (excitation spectrum, see Sect.8.2), whereas PM 2 records the dispersed fluorescence spectrum excited at a fixed laser wavelength, where the laser is stabilized... 

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