Kr laser

Most Ar and Kr lasers are CW. A gas pressure of about 0.5 Torr is used in a plasma tube of 2-3 mm bore. Powers of up to 40 W distributed among various laser wavelengths can be obtained. 

Nonresonance Raman spectra of the alternating LB films were measured by a total reflection method shown in Figure 23. The films were deposited on quartz prisms. The s-polarized beam of 647.1 nm from a Kr laser was incident upon the interface between the quartz and film at an angle of 45° from the quarz side, and totally reflected. Raman line scattered from the film in the direction of 45° from the surface was measured through a Spex Triplemate by a Photometries PM512 CCD detector with 512x512 pixels operated at -125 °C. The spectral resolution was about 5 cm 1. 

One of the most common and familiar examples of the neutral atom gas laser is the He-Ne laser. Examples of ionic gas lasers are the Ar+ or Kr+ lasers. The particular oscillating transitions and operation mechanisms can be found... 

Figure 2.10 The spectral dependence of the laser output power of Ar+ and Kr+ lasers.

Raman spectroscopy Raman spectra from small SWNT pieces with typical dimensions of 100 pm were recorded in the back-scattering geometry using two different micro-Raman setups comprised of a triple monochromator DILOR XY and a CCD detector system, cooled either to liquid nitrogen temperature or -100°C. The 488 or 514.5 nm line of an Ar+ laser, as well as the 647.1 nm line of a Kr+ laser, were used for excitation, while the beam intensity on the sample was =0.5 mW. The laser line was focused on the sample by means of a lOOx objective with a spatial resolution of 1 pm. 

The light source is a home made CM ring LD 700 dyo laser, pumped by a Kr+ laser. In the range 730-780 nm (wavelength of the two-photon 2S-nD transitions for n 8 it provides a power of about 1W on single mode operation. The frequency stabilization is made by locking the laser to an external auxiliary Fabry-Perot cavity indicated FPA in Fig.2 the resulting... 

The TCNQ- radical thus obtained is completely stable for at least 3 hr, and its electronic spectrum shows strong absorption bands between 950 and 550 nm. Thus, the RR spectrum of TCNQ-- was obtained by using the 647.1 nm line of a Kr+ laser (Fig. 3-20a). On the other hand, TCNQ has a strong absorption band near 400 nm. Therefore, its preresonance spectrum, shown in Fig. 3-20b, was obtained by the 457.9 nm line of an Ar+ laser. In both spectra, all strong and medium intensity bands were found to be polarized (totally symmetric). The vibrational frequency shifts in going from... 

The Raman spectra were recorded in the backscattering geometry on a Labram I (Jobin-Yvon, Horiba Group, France) microspectrometer in conjunction with a confocal microscope. To avoid any thermal photochemical effect, we have used a minimum intensity laser power on sample of 370 pW with the 514.5 nm incident line from an Ar-Kr laser from Spectra Physics. Detection was achieved with an air cooled CCD detector and a 1800 grooves/mm, giving a spectral resolution of 4 cm-1. An acquisition time of 120 s was used for each spectrum. The confocal aperture was adjusted to 200 pm and a 50 X objective of 0.75 numerical aperture was used. 

SERS spectra in Ag hydrosols were recorded using a Jobin-Yvon HG2S monochromator equipped with a cooled RCA-C31034A photomultiplier and a data acquisition facility. To reduce the thermal effects due to the laser light, a defocused beam with low power (20 mW) was used. Raman data were obtained with exciting lines supplied by Ar"- and Kr"- lasers (406.7, 413.1, 457.9, 488.0, 514.5, 520.8, 568.2, 647.1,676.4 nm) or by He-Ne laser (632.8 nm). AU spectra were corrected to account for monochromator and photomultiplier efficiency. Power density measurements were performed with a power meter instrument (model 362 Scientech, Boulder, CO, USA) giving 5% accuracy in the 300-1,000 run spectral range. 

The last line of Table 7.2 indicates the total optical output power for each ion laser, in terms of multiline visible power. However, this power is distributed among many wavelengths and is not useful directly for Raman spectroscopy. Multiline output is often used to pump dye lasers or titanium sapphire lasers, but these cases are fairly rare in analytical applications. Most often, a prism is added to the laser cavity to select one of the wavelengths listed in Table 7.2. As apparent in the table, Ar+ and Kr+ have a few strong lines that are popular for Raman (e.g., 488, 514.5, and 647.1 nm) plus several more at lower power. The mixed-gas Ar+/Kr+ laser provides less power but covers a wider range of visible wavelengths than Ar+ or Kr+ alone. 

Ultraviolet output is available from both Ar" " and Kr+ lasers, sometimes with relatively minor modification. For a conventional large-frame Ar+ laser, the... 

For the irradiation with the high energy at 248 nm (e), where a surface blackening is observed, no polymer could be detected, partially due to the low signal to noise ratio in the defocused mode, which is ten times less than for the focused mode. It was also not possible to detect bands which are specific for graphite species, even with the use of standard Raman experiments with the excitation wavelength of an Ar+ (or Kr+) laser. 

The fundamental vibrational frequencies of ethylene are at 3374, 3287, 1974, 729, and 612 cm At what wavelengths will these bands be observed for each of the exciting lines of the Ar-Kr laser—4880, 5145, 5682, and 6471 A Discuss the extent of spectral overlap if unfiltered laser light was used. 

Calculate the relative intensities of a Raman line when excited by each of the four lines from an Ar-Kr laser. 

Fig. 3. Diagram of continuous wave (cw) laser sources suitable for metalloprotein resonance Raman spectroscopy. The best quality spectra are provided by Ar, Kr, He-Ne, and He-Cd lasers operating at fixed frequencies (the lengths of the lines indicate the relative output for a given laser) throughout the visible and near-UV region. An intracavity frequency-doubled (ICFD) Ar laser has been developed with five useful cw excitation wavelengths in the far-UV region (257, 248, 244, 238, and 228.9 nm). The high-powered Ar and Kr lasers can also be used to pump dye lasers which are tunable between the near-UV and near-IR region. The cw Nd YAG laser with a fundamental at 1064 nm is the primary excitation source in FT Raman spectrometers.

At the opposite end of the spectrum, UV sources for CE-LIF are becoming increasingly popular. UV radiation is capable of inducing fluorescence in many intrinsic fluorophores, including a number of biologically relevant molecules. The frequency-doubled Ar-ion laser (257 nm) was one of the first examples reported of UV-excitation for CE-LIF, and yielded improvements in LODs for a number of substances, such as conalbumin (1.4 x 10 M). As another example, a frequency-doubled Kr laser operating at 284 nm has been used for the analysis of neuropeptides and small biomolecules, and exhibited LODs for tryptophan of 800 zmol. In addition to frequency-doubled ion lasers, a number of relatively inexpensive pulsed lasers such as frequency quadrupled YAG (266 nm), KrF (248 nm), and hollow-cathode metal vapor lasers have appeared, which provide deep-UV excitation (e.g., 224 and 248 nm). ... 

Excimer laser N2 laser Flashlamp Ar laser Kr laser Nd YAG laser A/2 530 nm X/y. 355 nm Copper-vapor laser... 

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