Spectroscopy sub-Doppler

Purely Rotational Coherence Effect and Time-Resolved Sub-Doppler Spectroscopy of Large Molecules, P. M. Felker, J. S. Baskin, and A. H. Zewail, J. Chem. Phys. 86,2460 and 2483... 

Baskin, J.S., Felker, P.M. and Zewail, A.H. (1987). Purely rotational coherence effect and time-resolved sub-Doppler spectroscopy of large molecules. II. Experimental, J. Chem. Phys., 86, 2483-2499. 

PURELY ROTATIONAL COHERENCE AND SUB-DOPPLER SPECTROSCOPY. Guided by the theoretical decay simulations of Fig. 46, the first unambiguous observation of thermally averaged rotational coherence effects was made for excitation and detection of the S, - S00° band of jet-cooled t-stilbene.47 Observed fluorescence decays are shown in Fig. 47 theory and experiment match very well. The recurrences associated with rotational coherence effects in fluorescence have been observed for a number of other species as well. Among these species are t-stilbene-, 2, t-stilbene-argon complexes,48 and t-stilbene-he-lium complexes.71 The recurrences allow the determination of the excited-state rotational constants to a high degree of accuracy. [For example, for t-stilbene we find j(B + C) to be 0.00854 + 0.00004 cm-1.] The indications are that with currently available temporal resolution, rotational coherence effects should be observable in a multitude of species and should allow the accurate determination of such species excited-state rotational constants. 

Photodissociation of PH3 at 193 nm into PH2 and H atoms leaves an energy of 22 000 cm" to be distributed among the products degrees of freedom. The H atom kinetic energy distribution was measured by sub-Doppler spectroscopy of the Lyman-a transition. The distribution peaks at rather low energies around 3500 cm" The corresponding distribution of the PH2... 

Fig. 4.5 Experimental setup for sub-Doppler spectroscopy in a collimated molecular beam. Photomultiplier PMl monitors the total undispersed fluorescence, while PM2 behind a monochromator measures the dispersed fluorescence spectrum. The mass-specific absorption can be monitored by resonant two-color two-photon ionization in the ion source of a mass spectrometer...

For molecules the line densities are much higher, and often the rotational structure can only be resolved by sub-Doppler spectroscopy. Limiting the collimation angle of the molecular beam below 2 x 10 rad, the residual Doppler width can be reduced to values below 500 kHz. Such high-resolution spectra with linewidths of less than 150 kHz could be, for instance, achieved in a molecular iodine beam since the residual Doppler width of the heavy I2 molecules, which is proportional to is already below this value for a collimation ratio 6 < 4 x 10 [400]. At... 

More examples of sub-Doppler spectroscopy in atomic or molecular beams can be found in reviews on this field by Jacquinot [396], and Lange et al. [401], in the two-volume edition on molecular beams by Scoles [402], as well as in [403 06],... 

With techniques of sub-Doppler spectroscopy, even small collisional broadening effects can be investigated with high accuracy. One example is the measurement of pressure broadening and shifts of narrow Lamb dips (Sect. 2.2) of atomic and molecular transitions, which is possible with an accuracy of a few kilohertz if stable lasers are used. The most accurate measurements have been performed with stabilized HeNe lasers on the transitions at 633 nm [975] and 3.39 um [976]. When the laser frequency co is tuned across the absorption profiles of the absorbing sample inside the laser resonator, the output power of the laser Pl(co) exhibits sharp... 

J.L. Hall, Sub-Doppler spectroscopy, methane hyperfine spectroscopy and the ultimate resolution limit, in Colloq. Int. due CNRS, vol. 217 (Edit, due CNRS, Paris, 1974), p. 105... 

P. Etman, O. Gustafssosn, P. Lindblom, A simple supersonic jet discharge source for sub-Doppler spectroscopy. Phys. Sen 38, 789 (1988)... 

For sub-Doppler spectroscopy, single-mode cw dye lasers represent the most important laser types besides cw tunable solid-state lasers. Great efforts have therefore been undertaken in many laboratories to increase the output power, tuning range, and frequency stability. Various resonator configurations, pump geometries, and designs of the dye flow system have been successfully tried... 

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