Strong Infrared Field Research Articles

Time dependence of multiphoton dissociation of molecules in a strong infrared field. Real-time measurement using a nanosecond laser source

The multiphoton dissociation of tetramethyldioxetane is accompanied by instantaneous visible light emission. The lifetime of the emitting species in this chemiluminescent reaction is very short (≈ 10 −9 s),allowing real time monitoring of the reaction rate. The reaction is found to consist of two distinct stages: a prompt one, occurring during the laser pulse, and a delayed one persisting long (a few microseconds) after laser pulse termination. The delayed reaction accounts for at least 90% of the products, even under conditions that would normally be considered collision free. The prompt reaction is studied using a nanosecond pulse train. It is found to follow closely the laser profile, but its onset is delayed with respect to the beginning of the laser train. This delay is a function of the laser energy, and independent of the laser power. The relationship between this delay and the threshold phenomenon usually observed with multiphoton dissociation reaction is discussed. The implications of the experimental results (particularly the predominance of the post-laser-pulse reaction) to the mechanism of multiphoton molecular dissociation is discussed.

Mechanism of the excitation of high vibrational–rotational states and dissociation of polyatomic molecules by an infrared field

The physical mechanism of the excitation of high vibrational–rotational states and dissociation of polyatomic molecules in a strong infrared field is discussed. It is shown that when the level density is high, the process can be quantitatively described using a system of rate equations. For simplicity this system is replaced by a diffusion-type partial differential equation. The solution of this equation is applied to estimate the threshold radiation pulse energy needed for dissociation.

Nature of "instantaneous" luminescence due to interaction of SiF4molecules with a strong infrared field

A spectral investigation was made of the luminescence resulting from the interaction of a strong infrared field (generated at different frequencies by a CO2 laser) with SiF4 molecules. The instantaneous state of the luminescence was not due to possible dissociation products of SiF4 but the later stage was due to the SiF radicals. The instantaneous luminescence spectrum was attributed to transitions between excited electronic states of the SiF4 molecule.

Tunable lasers and applications (Proc. Loen Conf., Norway, 1976)

A review is given of the Proceedings of the International Conference on Tunable Lasers and Applications which took place in Loen, Norway June 6?11, 1976 and were published by Springer Verlag, Berlin in 1976. The main results are reviewed under the following headings: I) tunable high-energy ultraviolet and visible lasers; II) tunable infrared lasers; III) isotope separation and laser chemistry; IV) nonlinear excitation of molecules by high-intensity infrared laser radiation; V) laser photokinetics; VI) atmospheric photochemistry and diagnostics; VII) photobiology; VIII) spectroscopic applications of tunable lasers. The following tendencies are identified in the design and application of tunable lasers: 1) development and studies of high-power tunable infrared lasers; 2) development of tunable ultraviolet excimer lasers; 3) intensification of studies of laser isotope separation by selective dissociation of molecules in a strong infrared field; 4) extensive work in laser spectroscopy; 5) application of laser methods to studies of biological objects.

Use of a tunable compressed-hydrogen Raman laser in isotope separation

The possibility of using a tunable far-infrared Raman laser in isotope separation by selective collisionless dissociation in a strong infrared field was demonstrated in the case of the SF6 molecule. The laser radiation was tuned to the combination vibration ν4 + ν5 = 1138 cm–1 of the 32SF6 molecule. After 60 pulses with a total energy of 25 J the residual gas became enriched with the 34S isotope by a factor of 1.06. The reaction products of the dissociated SF6 molecules were enriched with the 32S isotope by a factor of 1.25.

Laser separation of isotopes by dissociation of polyatomic molecules in a strong infrared field

Laser separation of isotopes by dissociation of polyatomic molecules in a strong infrared field