Laser intracavity

Silylene SiH2 was directly detected during the pyrolytic decomposition of silane (and ethylsilane EtSiII3) for the first time by intracavity laser spectroscopy in 198865. The high detection sensitivity of this experiment allowed the pyrolysis mechanism to be examined under conditions that optimized film growth rather than spectroscopic conditions. 

At certain positions in the flame, the background flame luminescence received by the photomultiplier tube can be 15% of the Rayleigh scattered intensity. A large reduction of this noise would be achieved by replacing the 1 nm bandpass filter with a monochrometer. Use of a multipass cell (12) or intracavity laser (13) would raise the signal above the flame luminescence. In addition, the increased scattered photon count rate would increase the precision of each measurement. 

Several species which are weak absorbers or which may not fluoresce readily, may be detected using intracavity laser absorption. This is a much more sensitive method of detection than the conventional absorption measurements because the output power of a laser is very sensitive to small variations in its gain which, in term, depends on the concentration of absorbing species within the cavity. Vibrational state populations for the CO produced in the reaction... 

Direct spectroscopic measurements of absorptions could provide substantial and much-needed complimentary information on the properties of BLMs. Difficulties of spectroscopic techniques lie in the extreme thinness of the BLM absorbances of relatively few molecules need to be determined. We have overcome this difficulty by Intracavity Laser Absorption Spectroscopic (ICLAS) measurements. Absorbances in ICLAS are determined as intracavity optical losses (2JI). Sensitivity enhancements originate in the multipass, threshold and mode competition effects. Enhancement factor as high as 106 has be en reported for species whose absorbances are narrow compared to spectral profile of the laser ( 10). The enhancement factor for broad-band absorbers, used in our work, is much smaller. Thus, for BLM-incorporated chlorophyll-a, we observed an enhancement factor of 10 and reported sensitivities for absorbances in the order of lO- (24). 

Figure 10 shows the schematics of the experimental setup used for intracavity laser absorption spectroscopy (ICLAS) of bilayer lipid membranes (BLMs). Simultaneous electrical and ICLAS measurements were carried out in a two-compartment container constructed from two 1 cm path lengths quartz cells (Figure 11). 

Figure 10. Schematics of the experimental setup for intracavity laser absorption spectroscopy (ICLAS). CD chopper driver PM power meter Mj, M2, M3, M4 spherical high reflection mirrors Mp = pump mirror MN monochromator PMT photomultiplier SP silicon photocell PC Pockels cell WF wedged filter LIA lock-in amplifier R recorder MS microscope OF optical fiber S sample (solution on BLM) IEM instruments for electrical measurements (see Figure 2).

In this section, we will review previous studies of the CH overtone spectroscopy of CD3H. There exist high-resolution, rotationally resolved, experimental data for the first three CH overtones ( uv,) with n = 2, 3, 4) in the infrared and near infrared region (91,94). In the visible region, there also exists data from photoacoustic laser spectroscopy (96,97) and from the intracavity laser absorption spectroscopy (ICLAS) technique, which provides absolute intensities (85,86). Compared to methane, analysis of the spectra is much easier for CD3H, because of the relatively isolated CH chromophore. 

The near-infrared electronic transition occurring in the region of 745 nm was originally assigned as connected to the ground state. O Brien et al. [OOOBr] have recorded and analyzed this transition using intracavity laser absorption spectroscopy and conclude that it occurs between two unknown excited states. 

Fig,4 Schematic diagram of an intracavity laser Stark spectrometer. PSD stands for phase sensitive detector, DVM for digital voltmeter, HV for high voltage, and MOD for modulation source. (Reproduced by permission from Journal of Chemical Physics, 1977 66, 127)... 

Fig. 1.14 Experimental arrangement for intracavity laser spectroscopy using a step-function pump intensity and a definite delay for the detection [13]...

It is therefore better to pump the intracavity laser with a step-function pump laser, which starts pumping at r = 0 and then remains constant (Fig. 1.13). The intracavity absorption is then measured at times t with 0 < t which are... 

A. Campargue, F. Stoeckel, M. Chenevier, High sensitivity intracavity laser spectroscopy applications to the smdy of overtone transitions in the visible range. Spectrochim. Acta Rev. 13, 69 (1990)... 

A.A. Kaschanov, A. Charvat, F. Stoeckel, Intracavity laser spectroscopy with vibronic sohd state lasers. J. Opt. Soc. Am. B 11, 2412 (1994)... 

V.R. Mironenko, V.I. Yudson, Quantum statistics of multimode lasing and noise in intracavity laser spectroscopy. Sov. Phys. JETP 52, 594 (1980)... 

E.A. Sviridenko, M.P. Erolov, Possible investigations of absorption line profiles by intracavity laser spectroscopy. Sov. J. Quantum Electron. 7, 576 (1977)... 

K. Strong, T. J. Johnson, G.W. Harris, Visible intracavity laser spectroscopy with a step-scan Fourier-transform interferometer. Appl. Opt. 36, 8533 (1997)... 

Applications So far, intracavity laser spectroscopy has been applied primarily to the detection of absorption spectra of gaseous impurities such as NH3 and CH4 in the near-infrared region using a tunable broadband laser. Special DLs designed with an external cavity have also been investigated recently for this purpose. CRS has been applied successfully to trace element detection using the ICP as the atomization system. The detection limits observed are at sub-parts per billion level (e.g., 0.3 ng ml for lead) and comparable to the detection limits achieved with ICP-MS. 

All the intracavity laser flux cannot be extracted because the RGH laser mixture contains many absorbers at the laser wavelength. The percent contribution of the absorption channel is shown in Fig. 8. Main absorbers seem to be... 

Cl and XeJ. The photon extraction efficiency, defined as the ratio of the extracted laser energy to the intracavity laser energy, is in excess of 70% here (see Fig. 6). This means that over 70% of the intracavity laser energy can be... 

The percent contributions of the KrF relaxation channels are shown in Fig. 10. Sixty to eighty percent of the KrF excimers can contribute to the stimulated emission as an intracavity laser flux, depending on the excitation rate. Other relaxation processes are by a slow electron, F2, Kr, and Ar. In these collisional relaxation reactions the reaction KrF + Kr forms the Kj 2F trimer, and the reaction KrF + Ar forms the ArKrF trimer. 

Handler KG, Harris RA, O Brien LC, O Brien JJ (2011) Intracavity laser absorption spectroscopy of platinum fluoride, PtF. J Mol Spectr 265 39- 6... 

In the case of a homogeneous profile g(v —vo)> all molecules in the upper level can contribute to stimulated emission at the laser frequency Ua with the probability Bikpgiva I d), see (5.8). Although the laser may oscillate only with a single frequency v, the whole homogeneous gain profile a(v) = ANa v) saturates until the inverted population difference AN has decreased to the threshold value AAthr (Fig- 5.23a). The saturated amplification coefficient asat(v) at the intracavity laser intensity / is, according to Sect. 3.6,... 

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