Collision-Free Infrared Multiphoton Dissociation of Silane

Makowe, Joachim; Boyarkin, Oleg V.; Rizzo, Thomas R.

doi:10.1021/jp002566f

Cited by 7 publications

(15 citation statements)

References 35 publications

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“…The apparatus we employ for these experiments, depicted schematically in Figure , has been described in detail elsewhere. , Briefly, we generate 3−4 mJ of infrared radiation at 4450.5 cm -1 for excitation of the first Si−H stretch overtone by difference frequency mixing the output of a Nd:YAG pumped dye laser with the fundamental of the same pump laser in a LiNbO 3 crystal. As a dissociating laser we use either a home-built NH 3 laser pumped by a pulsed CO 2 laser or the CO 2 laser directly.…”

Section: Methodsmentioning

confidence: 99%

Infrared Laser Chemistry of Trichlorosilane in View of Silicon Isotope Separation

Polianski¹,

Boyarkin²,

Rizzo³

et al. 2003

J. Phys. Chem. A

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With a view toward laser isotope separation of Si, we have studied infrared multiphoton dissociation (IRMPD) of room temperature trichlorosilane, SiHCl 3 . Over the wavelength range investigated, multiphoton dissociation of the room temperature species exhibits a maximum efficiency at 12.6 µm and a threshold fluence of only ∼1 J/cm 2 . Vibrational overtone preexcitation of SiHCl 3 to the first SiH-stretch overtone (2ν 1 ) prior to IRMPD results in a 10-fold increase of the dissociation yield compared to molecules with only thermal excitation. In an effort to collect the nascent SiCl 2 dissociation fragments, we have tested a number of different molecules that could serve as a scavenger to convert them into a stable gaseous compound. Several of these molecules react directly with trichlorosilane after being decomposed by collisional energy transfer from vibrationally excited SiHCl 3 and therefore are not suitable for a laser isotope separation process. Of the compounds tested, we find that only BCl 3 scavenges SiCl 2 without significant reaction with the starting material.

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Section: Methodsmentioning

confidence: 99%

Infrared Laser Chemistry of Trichlorosilane in View of Silicon Isotope Separation

Polianski¹,

Boyarkin²,

Rizzo³

et al. 2003

J. Phys. Chem. A

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“…Implementation of such a scheme for SiH 4 is complicated by the lack of rotational assignments of the first Si−H stretch overtone band of silane. Moreover, our previous investigations revealed that efficient IRMPD of vibrationally pre-excited SiH 4 using a particular line of a NH 3 laser occurs only if the first laser pre-excites the molecules to a particular rotational state . We attribute this selectivity to the requirement that the first few steps of IRMPD be nearly resonant with the frequency of the NH 3 laser when the dissociating fluence is low.…”

Section: Introductionmentioning

confidence: 90%

“…In contrast, when the molecules are pre-excited to the first Si−H stretch vibrational overtone before IRMPD, the dissociation is more efficient and exhibits lower threshold fluence. We estimate that vibrational pre-excitation increases the dissociation cross-section by a factor of 230 …”

Section: Introductionmentioning

confidence: 97%

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Isotopically Selective Infrared Multiphoton Dissociation of Vibrationally Excited SiH₄

2002

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We use mass-resolved 2+2 resonantly enhanced multiphoton ionization (REMPI) of silicon atoms to detect isotopically selective infrared multiphoton dissociation (IRMPD) of both ground-state and vibrationally pre-excited SiH4. To demonstrate that the detection scheme provides a faithful monitor of the isotopic composition of the primary dissociation products, this approach was first tested on the products generated by both IRMPD and UV photodissociation of phenylsilane. It was then employed to evaluate the degree of isotopic enrichment achieved by IRMPD of ground-state silane using an ammonia laser for dissociation. In a second type of experiment, silane molecules are pre-excited to the first overtone of the Si−H stretch, and then dissociated selectively with the ammonia laser. We find that pre-excitation increases the dissociation cross section by a factor of 230. Tuning the overtone pre-excitation laser while collecting the mass-resolved silicon ion signal generates an overtone excitation spectrum of SiH4 that is sorted by the silicon isotope. Certain combinations of overtone pre-excitation and ammonia laser dissociation frequencies lead to a high level of isotopic enrichment in the dissociation products: >99% in 28Si or 29Si, and >96% in 30Si. We evaluate the practicality of an overtone-pre-excitation/IRMPD scheme for silicon isotope separation on a macroscopic scale.

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“…The IRLAPS detection technique has been used over the past decade for measuring spectra of highly vibrationally excited molecules such as CF 3 H, 17,18 SiH 4 , 19,20 and methanol, 12,[21][22][23] and the experimental details have been previously described. 21,24 -27 We briefly summarize this technique as applied to the present experiments.…”

Section: Experimental Approachmentioning

confidence: 99%

Torsion–rotation analysis of OH stretch overtone–torsion combination bands in methanol

Rueda

Boyarkin

Rizzo

et al. 2002

The Journal of Chemical Physics

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We report rotationally resolved spectra of jet-cooled methanol for the OH stretch overtones, 2v 1 and 3v 1 , and for the torsional combinations, 2v 1 ϩv 12 , 2v 1 ϩ2v 12 , 3v 1 ϩv 12 , and 3v 1 ϩ2v 12 . The spectra are obtained by direct excitation from the vibrational ground state with an infrared laser pulse. Population in the resulting upper state levels is detected by infrared laser assisted photofragment spectroscopy ͑IRLAPS͒. Global fits of the spectra to the Herbst Hamiltonian yield the torsional and rotational parameters, including F, , V 3 , and V 6 , for each OH stretch excited state. For each quantum of OH stretch excitation, we find that the torsional barrier height V 3 increases by 40.9Ϯ1.9 cm Ϫ1 and the torsional inertial F decreases by 0.89Ϯ0.02 cm Ϫ1 . With reference to ab initio calculations, we explain the increase in V 3 in terms of changes in the electronic structure of methanol as the OH bond is elongated. For ⌬v 12 ϭ1 we observe only transitions with ⌬KϭϮ1, and for ⌬v 12 ϭ2 we observe only ⌬Kϭ0. We present a Franck-Condon model to explain these apparent selection rules and the overall pattern of intensity.

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Collision-Free Infrared Multiphoton Dissociation of Silane

Cited by 7 publications

References 35 publications

Infrared Laser Chemistry of Trichlorosilane in View of Silicon Isotope Separation

Infrared Laser Chemistry of Trichlorosilane in View of Silicon Isotope Separation

Isotopically Selective Infrared Multiphoton Dissociation of Vibrationally Excited SiH₄

Torsion–rotation analysis of OH stretch overtone–torsion combination bands in methanol

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Collision-Free Infrared Multiphoton Dissociation of Silane

Cited by 7 publications

References 35 publications

Infrared Laser Chemistry of Trichlorosilane in View of Silicon Isotope Separation

Infrared Laser Chemistry of Trichlorosilane in View of Silicon Isotope Separation

Isotopically Selective Infrared Multiphoton Dissociation of Vibrationally Excited SiH4

Torsion–rotation analysis of OH stretch overtone–torsion combination bands in methanol

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Isotopically Selective Infrared Multiphoton Dissociation of Vibrationally Excited SiH₄