Fluorescence intermodulated

The reaction of elemental phosphorus with hydrogen was also used for PH2 production. H atoms from MW-discharged H2 were passed over the red modification, and the resulting PH2 was detected by LIF [51, 52], IMF (intermodulated fluorescence) [27], or MW spectroscopy [14]. The reaction of phosphorus vapor with atomic or molecular hydrogen did not lead to any PH2 electronic emission [18]. Emission bands, which had been observed during the reaction of elemental P with atomic H, were first attributed to PH2 [53,54], but they were later shown to be due to HPO [55]. 

A complete set of magnetic hf coupling constants and the P nuclear spin-rotation interaction constants (all in MHz) were obtained from an analysis of the hf structure of twelve lH(total H nuclear spin) = 0 and fourteen Ih=1 rovibronic lines of the A (0, 0, 0) X (0, 0, 0) band. An Intermodulated fluorescence (IMF) method was applied, which was first shown in [17] to be able to eliminate the Doppler width. A dye laser was employed as a source. Ground state constants were taken from a preliminary publication of [3] (T c was obtained with the sum rule) [6] ... 

Tables in the present chapter contain in their upper part data on the spin-rotation interaction constants e q (q = Inertial axes a, b, c) and In their lower part data on the rotational constants A, B, and C. Methods of measurement, references, and remarks are the same for either constant. The quartic (A, 8 and A, 5) and sextic (O, (p) centrifugal distortion constants listed In the first table (for the electronic ground state of PHg) are defined by the A-reduced form (asymmetric reduction) of the respective Hamiltonian for spin-rotation Interaction and rotation [1 to 3]. Abbreviations used in the tables are MW for microwave absorption, EL AB for electronic absorption, LMR for laser magnetic resonance, FIR for far IR, IMF for Intermodulated fluorescence.

Fig. 2.13 Intermodulated fluorescence method for saturation spectroscopy at small densities of the sample molecules (a) experimental arrangement (b) hyperfine spectrum of the v" = 1,...

The experimental performance is depicted in Fig. 2.18. The modulation frequency = 2nf is tripled by forming rectangular pulses, where the third harmonic is filtered and fed into the reference input of a lock-in amplifier that is tuned to 3f2. Figure 2.19 illustrates this technique by the third-derivative spectrum of the same hfs components of I2 as obtained with the intermodulated fluorescence technique in Fig. 2.13. 

The sensitivity is 2-3 orders of magnitude larger than that of saturation spectroscopy. It is surpassed only by that of the intermodulated fluorescence technique at very low sample pressures (Sect. 2.3.1). 

The Doppler-broadened baekground with the residual Doppler width from the divergence of the molecular beam ean completely be eliminated by chopping the two laser beams at two different frequeneies fi, fi, and monitoring the signal at the sum frequency /i -I- /2 (intermodulated fluorescence. Sect. 2.3.1). This is demonstrated by the insert in Fig. 4.25. The linewidth of the Lamb dips in Fig. 4.25 is below 1 MHz and is mainly limited by frequeney fluctuations of the cw single-mode dye laser [453],... 

M.S. Sorem and A.L. Schawlow, Saturation Spectroscopy in molecular iodine by intermodulated fluorescence, Opt. Common. 5 148 (1972). 

The Doppler-broadened background with the residual Doppler width from the divergence of the molecular beam can completely be eliminated by chopping the two laser beams at two different frequencies /i, /2, and monitoring the signal at the sum frequency f + fi (intermodulated fluorescence,... 

Fig.9.46. Experimental arrangements for intermodulated fluorescence spectroscopy (left) and intermodulated opto-galvanic spectroscopy (right) [9.178]...

A single-mode cw dye laser can be used for measurements of this kind. The experimental set-up is similar to the one used in Doppler-free intermodulated fluorescence measurements (Sect.9.5.2), but now the beams are presented to the atoms/molecules one at a time. For measurements of this kind, the flow can be seeded with sodium atoms or I2 molecules. Imaging measurements using array detectors, as discussed above, can be performed. In [10.19-21,54] imaging measurements of species concentrations, temperatures and flows utilizing LIF have been described. 

Fig. 9.60. Gompaxing recordings of the 5882 A Ne line using POLINEX upper curve) and intermodulated fluorescence spectroscopy [9.374]...

Dye laser intermodulated fluorescence. Sign from [84But] where circularly polarized light was employed. 

Fig. 10.19. OODR spectroscopy in a collimated molecular beam with overlapping pump and probe beam and detection at the sum frequency (intermodulated fluorescence) [10.39]...

V" = 1, J" = 98) (v = 58, J = 99) in the iodine molecule I2 [10.34]. The two laser beams were chopped by a rotating disc with two rows of a different number of holes which interrupted the beams at f = 600 s" and f2 = 900 s". The upper spectrum was monitored at the frequency f at which the pump beam was chopped while the probe was not modulated. The Doppler-broadened background caused by the linear terms in (10.25) and the Lamb-dips both show a modulation at the frequency f and are therefore recorded simultaneously. The center frequencies of the hfs components, however, can be obtained more accurately from the intermodulated fluorescence spectrum (lower spectrum) which was monitored at the sum frequency + f2) where the linear background is suppressed. 

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