Infrared laser spectroscopy of molecular beams

Gough, T. E.; Miller, R. E.; Scoles, G.

doi:10.1063/1.89390

Cited by 271 publications

(64 citation statements)

References 6 publications

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“…Recent work on a model system [118] has found that the hydrodynamic and this molecular rotor based fixed node approximation are closely related, and break down at about the same point when the rotational constant of the molecule is increased. To date, the diffusion Monte Carlo calculations have been published only for SF 6 , so the accuracy of the method in general is hard to judge, though it is likely the most accurate of the presently available methods.…”

Section: Changes In Rotational Constants: How Is the Helium Moving?mentioning

confidence: 99%

“…For HCN and HCCH, which have small moments inertia, the hydrodynamic calculations significantly overestimate the observed increase which is taken as evidence of the breakdown of the adiabatic following (see below). Kwon et al [107] have reported that the hydrodynamic model predicts for SF 6 an increase in the moment of inertia of only 6(9)% of the experimentally observed value when their calculated superfluid (total) helium solvation density was used. Similar hydrodynamic calculations have been done by Lehmann and Callegari [116] using the lowest four tensor components in the expansion of the helium density in octahedral harmonics.…”

Section: Changes In Rotational Constants: How Is the Helium Moving?mentioning

confidence: 99%

“…This leaves bolometric detection of the energy deposited in the beam by a resonant, tunable laser as the method of choice for this type of spectroscopy [6]. Assuming unity partition function and full saturation of the IR transition, it can be shown that with a seeded beam of "standard" intensity and the typical sensitivity of a doped Si (or Ge) bolometer operating at 1.5 K (noise equivalent power on the order of 100 fW/ √ Hz), signalto-noise (S/N) ratios of up to 10 5 can be obtained [5].…”

Section: Introduction a Scope Of The Reviewmentioning

confidence: 99%

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Helium nanodroplet isolation rovibrational spectroscopy: Methods and recent results

Callegari¹,

Lehmann²,

Schmied³

et al. 2001

The Journal of Chemical Physics

350

459

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In this article, recent developments in HElium NanoDroplet Isolation (HENDI) spectroscopy are reviewed, with an emphasis on the infrared region of the spectrum. We discuss how molecular beam spectroscopy and matrix isolation spectroscopy can be usefully combined into a method that provides a unique tool to tackle physical and chemical problems which had been outside our experimental possibilities. Next, in reviewing the experimental methodology, we present design criteria for droplet beam formation and its seeding with the chromophore(s) of interest, followed by a discussion of the merits and shortcomings of radiation sources currently used in this type of spectroscopy. In a second, more conceptual part of the review, we discuss several HENDI issues which are understood by the community to a varied level of depth and precision. In this context, we show first how a superfluid helium cluster adopts the symmetry of the molecule or complex seeded in it and discuss the nature of the potential well (and its isotropy) that acts on a solute inside a droplet, and of the energy levels that arise because of this confinement. Second, we treat the question of the homogeneous versus inhomogeneous broadening of the spectral profiles, moving after this to a discussion of the rotational dynamics of the molecules and of the surrounding superfluid medium. The change in rotational constants from their gas phase values, and their dependence on the angular velocity and vibrational quantum number are discussed. Finally, the spectral shifts generated by this very gentle matrix are analyzed and shown to be small because of a cancellation between the opposing action of the attractive and repulsive parts of the potential of interaction between molecules and their solvent. The review concludes with a discussion of three recent applications to (a) the synthesis of far-fromequilibrium molecular aggregates that could hardly be prepared in any other way, (b) the study of the influence of a simple and rather homogeneous solvent on large amplitude molecular motions, and (c) the study of mixed 3 He/ 4 He and other highly quantum clusters (e.g., H2 clusters) prepared inside helium droplets and interrogated by measuring the IR spectra of molecules embedded in them. In spite of the many open questions, we hope to convince the reader that HENDI has a great potential for the solution of several problems in modern chemistry and condensed matter physics, and that, even more interestingly, this unusual environment has the potential to generate new sets of issues which were not in our minds before its introduction.

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Section: Changes In Rotational Constants: How Is the Helium Moving?mentioning

confidence: 99%

Section: Changes In Rotational Constants: How Is the Helium Moving?mentioning

confidence: 99%

Section: Introduction a Scope Of The Reviewmentioning

confidence: 99%

See 1 more Smart Citation

Helium nanodroplet isolation rovibrational spectroscopy: Methods and recent results

Callegari¹,

Lehmann²,

Schmied³

et al. 2001

The Journal of Chemical Physics

350

459

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“…High resolution spectra can be obtained from measurements on supersonic expansions (Gough et al 1977;Miller 1980), but bulk gas meas urements show only a broad rotational-vib rational band structure. One method for modelling the second situation is to artificially broaden the transitions predicted by a normal mode analysis.…”

Section: Introductionmentioning

confidence: 99%

The Infrared Absorption Spectrum of Water

Coker¹,

Reimers²,

Watts³

1982

Aust. J. Phys.

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A combination of quantum calculations and Monte Carlo methods is used to predict the infrared absorption spectrum of the water monomer, water dimer and the pure liquid. Full quantum calculations using internal coordinates are used to fit three Morse oscillators to the fundamental and overtone vibrations of the water monomer. This intramolecular potential is then combined with an accurate intermolecular surface to calculate the dimer spectrum from a normal mode analysis and from classical trajectory studies. The liquid state spectrum is obtained using a Monte Carlo simulation program together with a sequence of normal mode analyses of representative molecular configurations. Results are in good agreement with available experimental data suggesting that the potential energy surfaces used are reasonably accurate.

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“…1. The system consists of a Kr' laser pumped Burleigh FCL-20 color center laser, diagnostic box, bolometric molecular beam detector (9), and a Micromation 2-64 microcomputer used to synchronously scan1 the three tuning elements, (grating, 21.6 GHz internal etalon and folding mirror) of the color center laser necessary to provide broadband single frequency scanning of the spectrometer. For these experiments, 0.9 W of 6471 A Kr' laser output was used to pump a RbCI: Li color center crystal producing 0.17-0.85 mW of continuously tunable single frequency laser output power from 3338-3284 cm-' which could be tuned over segments of 2 30 cm-' at a time.…”

Section: Methodsmentioning

confidence: 99%

Broadband v₃ sub-Doppler spectrum of HCN: application of a color center laser optothermal molecular beam spectrometer

Kyrö¹,

Shoja-Chaghervand²,

Eliades³

et al. 1985

Can. J. Chem.

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A broadband v, sub-Doppler spectrum of HCN has been recorded in the range 3340-3280 cm-' using a single frequency continuously scanable computer-controlled color center laser optothermal molecular beam spectrometer. Absolute frequencies for rovibrational transitions R(9) through P(9) have been determined to an accuracy 5 20 MHz or 2 parts in lo7. An unconstrained five-parameter fit to this datum results in molecular constants: B" = 1.47822146 (182) IntroductionThe rovibrational v, spectrum of HCN is an important secondary frequency standard ( I ) in the 3 Fm region and for this reason has been the subject of numerous rovibrational analyses using both classical and laser spectroscopic methods (2-4). Although high resolution spectra do exist for isolated transitions in this band (5, 6), most previous studies have, however, been carried out in the gas phase under situations in which Doppler and pressure broadening often result in transition overlap and consequently inaccuracies in frequency determination. Although very accurate ground and excited state microwave rotational spectra (7) are available for J 0 + 1; 1 + 2, 2 + 3, 00'0 and J 0 + 1, 1 + 2, 2 + 3 and 3 + 4, 00°1, states absolute rovibrational transition frequencies accurate to 5 30 MHz have not been determined for frequency calibration purposes.' The advent of broadly tunable single frequency color center

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Infrared laser spectroscopy of molecular beams

Cited by 271 publications

References 6 publications

Helium nanodroplet isolation rovibrational spectroscopy: Methods and recent results

Helium nanodroplet isolation rovibrational spectroscopy: Methods and recent results

The Infrared Absorption Spectrum of Water

Broadband v₃ sub-Doppler spectrum of HCN: application of a color center laser optothermal molecular beam spectrometer

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Infrared laser spectroscopy of molecular beams

Cited by 271 publications

References 6 publications

Helium nanodroplet isolation rovibrational spectroscopy: Methods and recent results

Helium nanodroplet isolation rovibrational spectroscopy: Methods and recent results

The Infrared Absorption Spectrum of Water

Broadband v3 sub-Doppler spectrum of HCN: application of a color center laser optothermal molecular beam spectrometer

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Broadband v₃ sub-Doppler spectrum of HCN: application of a color center laser optothermal molecular beam spectrometer