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  • 1
    Electronic Resource
    Electronic Resource
    Silicon carbide formation by annealing C60 films on silicon (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 6141-6146 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Silicon carbide films were grown on (100) silicon substrates by deposition of 200-nm-thick C60 films, followed by annealing. The predeposited C60 is progressively destroyed by annealing, and carbon reacts with silicon to produce SiC. The reaction starts at the interface and continues by diffusion of silicon through the already formed SiC. At the lower temperatures (700 °C), the reaction is localized at the interface. Diffusion of silicon and formation of stoichiometric SiC requires annealing at 800 °C for t≥100 min and at 900 °C for t≥25 min. The stoichiometric films are uniform with a grain size of 20–40 nm. A diffusion coefficient of silicon in SiC of 4×10−15 cm2/s at 900 °C was determined. Because the diffusion of silicon is faster through preferential paths in the SiC film, such as grain boundaries and other crystalline defects, pits and voids are produced in the silicon substrate when the C60 predeposited film covers larger areas. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364395
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  • 2
    Electronic Resource
    Electronic Resource
    Rotational spectra and structures of small clusters containing the HCN dimer: (HCN)2–Ar, a T-shaped trimer (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 1557-1563 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Microwave rotational spectra have been observed for the four 14N/15N isotopic species of an (HCN)2–Ar trimer with the pulsed nozzle Fourier transform method using the Flygare Mark II spectrometer. Thirteen J→J' asymmetric top transitions were measured in the 2.5 to 10 GHz region for the parent 14N,14N trimer and nine for each of the other three species. The 14N nuclear quadrupole hyperfine structure was analyzed for the transitions and the interaction constants and line centers determined. The line centers were fitted to obtain ground vibronic state rotational and quartic centrifugal distortion constants. For the 14N/14N trimer these are (in MHz) for A‘, B‘, and C‘: 2013.5993(10), 1759.2756(3), 932.3709(2); and for τ1, τ2, τaaaa, τbbbb, and τcccc@B: −0.3017(1), −0.0660(1), −0.1700(9), −0.013 71(1), and −0.0088(1). The inertial defect is 3.7881 amu A(ring)2. The zero-point vibrationally averaged geometry is planar and T shaped with the structure of the linear HCN dimer remarkably unperturbed by presence of the Ar atom. The substitution N⋅⋅⋅N distance in the cluster is 4.453 A(ring) compared with 4.461 A(ring) in the free dimer. The argon is attracted by the π electrons of the two –C≡N groups, being equidistant from them. The Ar⋅⋅⋅N(1) and Ar⋅⋅⋅N(2) distances are 3.671 and 4.316 A(ring), respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454135
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  • 3
    Electronic Resource
    Electronic Resource
    Rotational spectrum and structure of the Ar3–HCl symmetric top (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 4383-4387 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Ar3–HCl tetramer has been identified via the observation of its microwave rotational spectrum using the pulsed nozzle Fourier transform technique. The rotational spectroscopic constants of the ground vibrational state have been obtained for the 35Cl/37Cl isotopes from measurements of the J=1→2 to J=4→5 transitions and their hyperfine structure. For Ar3–H35Cl, the values found for B0, DJ, DJK, and χaa are 843.8974(1) MHz, 2.333(2) and 1.818(6) kHz, and 31.006(5) MHz, respectively, and for Ar3–H37Cl, 825.9811(2) MHz, 2.211(5) and 1.940(12) kHz, and 24.481(8) MHz. The cluster is a symmetric top with the HCl along the C3 axis, its H end directed towards the Ar3 trimer. In its torsional oscillations, the HCl makes an average angle of 36.91° with the symmetry axis. The chlorine isotopic substitution leads to values of 3.8510 and 4.0024 A(ring) for the Ar–Ar and Ar–Cl distances. The results of the present study are compared with those reported earlier for the Arm–HF (m=1,2,3) and Arm–HCl (m=1,2) clusters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452898
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  • 4
    Electronic Resource
    Electronic Resource
    Rotational spectra and structures of the Ar2–H35Cl/37Cl trimers (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 5315-5322 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Microwave rotational spectra have been observed for both Cl isotopes of the Ar2–HCl trimer with the pulsed nozzle Fourier transform method using the Flygare Mark II spectrometer. The Cl nuclear quadrupole hyperfine structure was analyzed for each of the transitions and the coupling constants and line centers determined. Sixteen transitions were observed in the 2 to 15 GHz region for the 35Cl species and 11 for 37Cl. The line centers were fitted to obtain ground state rotational and quartic centrifugal distortion constants A‘, B‘, C‘, τ1, τ2, τaaaa, τbbbb, and τcccc. For Ar2–H35Cl, the values are 1733.857, 1667.932, 844.491, −0.1170, −0.0292, −0.1199, −0.0802, and −0.0079 MHz, respectively, and for Ar2–H37Cl: 1733.824, 1606.877, 828.497, −0.1121, −0.0279, −0.1205, −0.0737, and −0.0075 MHz. The equilibrium geometry is determined to be T shaped with C2v symmetry and the H end of the HCl closest to the Ar2. Large amplitude slightly anisotropic torsional motion of the HCl is evident from the hyperfine constants. The chlorine isotopic substitution enables the torsional displacement of the Ar2 dimer to be estimated. It is found to be an average of 7.3° with respect to the b axis. With allowance for the torsional effects, a value of 3.861 A(ring) is obtained for the Ar–Ar distance and 4.005 A(ring) for the Ar to Cl distance. An approximate, harmonic force field analysis is based on the centrifugal distortion constants. A comparison is given of the force constants and Ar–Ar distances for the Ar2–HCl and Ar2–H/DF trimers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452556
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  • 5
    Electronic Resource
    Electronic Resource
    Rotational spectra, dipole moment, and structure of the SiF4–NH3 dimer (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 3441-3446 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotational spectra of several isotopic species of the SiF4–NH3 dimer were obtained with the Mark II Flygare–Balle FT-MW spectrometer. This is the first determination of the gas phase structure of a penta-coordinated silicon. The spectra indicate a symmetric top, trigonal bipyramid SiF3N structure with the lone electron pair of the NH3 pointed at one face of the SiF4 and the three equatorial F's splayed significantly away from the N. The (angle)Fax–Si–Feq is about 12° less than tetrahedral. The Si–N distance is determined to be 2.090 A(ring). The experimental results are in excellent agreement with the SiF4 deformation predicted by the ab initio calculations of Rossi and Jasinski [Chem. Phys. Lett. 169, 399 (1990)]. The measured dipole moment is 5.61 D, an enormous enhancement compared to the sum of the monomer moments, 1.47 D. The increase of 4.14 D is due largely to the geometric distortion of the tetrahedral SiF4 molecule upon dimer formation, demonstrating that the Si–F bond is much more ionic than covalent. If the charge is simply partitioned between Si and F so as to obtain a moment of 4.14 D, the Si has a charge of +3.52 and each F, −0.88. This conclusion is consistent with recent applications of the atoms-in-molecules charge partition methodology developed by Bader and co-workers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461947
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  • 6
    Electronic Resource
    Electronic Resource
    Mutual polarization of monomer charge distribution in (HCN)2, (HCN)3, and (HCN)∞ (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 2717-2722 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A simple classical mutual polarization model accurately predicts the induced dipole moments of linear HCN dimer and trimer. The model employs the first four nonzero electrical molecular moments of each HCN, and both the molecular polarizability and the C–H and C–N bond dipole polarizabilities. The model is extended to linear H-bonded oligomers up to the pentamer, and also to an infinite linear H-bonded chain, appropriate for comparison with the H-bonded chains present in the HCN crystal. For the dimer and trimer, a relation is seen between the change in the electric field gradient at the N of HCN and the calculated induced C–N bond dipole moment. A semiquantitative proportionality constant, derived based on this relation, is used to enhance understanding of the underlying cause of the large increase in the 14N quadrupole coupling constant in the HCN crystal relative to the free HCN monomer. This increase results from the strong polarization of the C–N bond by the local field at each HCN caused by the rest of the HCN crystal lattice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459847
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  • 7
    Electronic Resource
    Electronic Resource
    Rotational spectra and structures of small clusters containing the HCN dimer: (HCN)2–Y with Y=HF, HCl, HCF3, and CO2 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4069-4078 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Microwave rotational spectra have been observed for a number of isotopic species of the (HCN)2–HF, –HCl, –HCF3, and –CO2 trimers. The observations were made with the pulsed nozzle, Fourier transform, Flygare/Balle Mark II spectrometer. The trimers have structures which are composites of the linear (HCN)2 dimer and the HCN–Y dimers, the latter linear for Y=HF and HCl, a symmetric top for Y=HCF3, and T-shaped with C2v symmetry for Y=CO2. The rotational constants for the most abundant species of each trimer are as follows: For Y=HF and HCl, B0 is 699.204 and 467.408 MHz, respectively, and DJ is 162 and 87 Hz; for Y=HCF3, B0 is 305.742 MHz and DJ and DJK are 51 and 471 Hz; for Y=CO2, treated as a symmetric top, (B0+C0)/2 is 452.426 MHz and DJ is 1.057 kHz. Hyperfine interaction constants were determined for several species. The B0's for each trimer were analyzed by a combination of isotopic substitution and fitting procedures to determine the distances r1 and r2 between the centers of mass (c.m.) of adjacent monomers. The B0's are relatively insensitive to the position of the central HCN but give r1+r2 accurately. With this limitation, r1 and r2 in the trimers are compared with the corresponding distances in the dimers, which are longer. For Y=HF, HCl, HCF3, and CO2, respectively, the shrinkages found in r1 are 0.069, 0.054, 0.030, and 0.004 A(ring) and in r2, 0.043, 0.062, 0.042, and 0.052 A(ring). The shrinkage in r1 and several other properties of the trimers exhibit some correlation with the pseudodiatomic stretching force constant in the HCN–Y dimer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456661
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  • 8
    Electronic Resource
    Electronic Resource
    Rotational spectrum and structure of the linear CO2–HCN dimer: Dependence of isomer formation on carrier gas (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4216-4221 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A linear hydrogen-bonded dimer, OCO–HCN, has been identified and characterized via its microwave rotational spectrum. The study was made using the pulsed nozzle Fourier transform method with the Flygare/Balle Mark II spectrometer. A T-shaped HCN–CO2 dimer was reported earlier by the Klemperer group. Rotational constants have been determined for all seven monoisotopically substituted species of the linear form. B0 , DJ , and χaa (14 N) for the normal isotopic dimer are 1057.9397(2) MHz, 1.372(8) kHz, and −4.2466(5) MHz, respectively. The average torsional displacements of the OCO and HCN monomers about their center of mass (c.m.) are found to be 7.66° and 12.40°, based on the substitution O–C and C–N bond distances for the dimer. With these values for α and γ, the B0 for the normal isotopic dimer corresponds to a c.m. to c.m. distance R=5.035 A(ring). Bending and stretching force constants and the well depth (ε∼590 cm−1 ) are estimated from the centrifugal distortion. The relative concentrations of the linear and T-shaped isomers are unusually sensitive to the carrier gas used in the supersonic jet expansion. The linear form could not be detected at all with argon as the carrier gas but gave a strong signal in neon first run (70% Ne, 30% He). In contrast, the T form gave strong signals in both carrier gases. However, a carrier-gas effect was not found for the N2 O/HF dimer pair, which has a high barrier between the bent NNO–HF and linear FH–NNO isomers. Similar results were obtained for chlorocyclohexane (CCH) and ethyl formate (EF), which have two conformational isomers. In CCH which has a high barrier to a↔e interconversion, the two conformers gave strong signals in both Ar and He. In EF, with a low barrier, the gauche conformer could not be detected in Ar but gave a strong signal in He, while the trans form gave strong signals in both carrier gases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455778
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  • 9
    Electronic Resource
    Electronic Resource
    Rotational spectrum and structure of the linear HCN trimer (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 138-148 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Microwave rotational spectra have been observed for 22 isotopic species of an HCN, hydrogen-bonded trimer with the pulsed nozzle, Fourier transform method using the Flygare/Balle Mark II spectrometer. The 14N nuclear quadrupole hyperfine structure was analyzed and the interaction constants and line centers determined. The line centers were fitted to obtain ground vibronic state rotational constants. For the normal isotopic species of (HCN)3, B0 was found to be 469.3073(1) MHz and DJ, 82.6(1) Hz. The quadrupole coupling constants χ(n) are −4.049(2), −4.251(2), and −4.375(1)MHz for n=1, 2, and 3, respectively, in HCN(1)HCN(2)HCN(3). The trimer has a linear or very near linear equilibrium structure. The B0's are insensitive to the position and torsional oscillations of the central HCN but they determine the outer HCNs quite accurately. An isotopic substitution method gives R, the c.m. distance between the outer HCN's, to be 8.790 A(ring) in the 14–14–14 species. A slightly smaller value 8.788 A(ring) is obtained from a fit of the B0's which includes the effects of isotopic substitution on the H/D–C and C–N bond lengths in the monomer. The distance between c.m.(1) and c.m.(2) may be somewhat shorter (∼0.01 A(ring)) than that between c.m.(2) and c.m.(3). The average c.m. separation in the trimer (4.395 A(ring)) is halfway between that of the dimer (4.447 A(ring)) which is known to be linear and the infinite linear chains in the solid (4.34 A(ring)). It is shown that the smaller quadrupole coupling constants in the trimer compared to the monomer are caused by a combination of torsional and charge redistribution effects. The torsional vibrations have average angular displacements of 12.60° and 8.55° for HCN(1) and HCN(3). The charge redistribution effect upon χ in the trimer (6.5%) is about 1.8 times that in the HCN dimer. The dipole moment of the trimer was found to be 10.6 D, a value enhanced by 1.8 D over the vector sum of the three vibrating monomers (8.83 D), an enhancement about 1.7 times that of the dimer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455515
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  • 10
    Electronic Resource
    Electronic Resource
    Rotational spectra and structures of the OC– and H3N–HCN–HF trimers: Coaxial mixing nozzle for reactive species (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 6971-6976 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotational spectra are reported for several isotopic species of the OC–and H3N–HCN–HF heterotrimers, detected with a pulsed nozzle, Fourier transform, Balle/Flygare microwave spectrometer. Rotational constants for the main isotopic species of the OC trimer are a B0 of 615.574 MHz and DJ of 251 Hz, and for H3N, a symmetric top, a B0 of 1067.161 MHz and DJ and DJK of 0.40 and 63 kHz. Their structures are composites of those reported for the X–HCN and HCN–HF dimers. They are effectively axially symmetric but have some shrinkage from the distances in the dimers. The shrinkages found in r1, the c.m. to c.m. distance for X–HCN are 0.070 and 0.098 A(ring) for X=OC and H3N, respectively, and in r2 for HCN–HF, 0.033 and 0.027 A(ring). The 14N and H–F hyperfine interactions in OC–HCN–HF are the same as those reported for the HCN–HF dimer. Detection of the X=OC and H3N trimers out of the many species possible required care in their generation. Both were favored by the strongly bonded HCN–HF subunit. The OC–HCN–HF was further enhanced by using a high concentration of CO in the gas expansion. For H3N–HCN–HF a coaxial mixing nozzle was developed to avoid the formation of NH4F(s). The selectivity and simplicity of the nozzle should be helpful in extending the range of species observable with pulsed nozzles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459473
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