The microwave spectrum,substitution structure and dipole moment of cyanobutadiyne,HCCCCCN

Cyanobutadiyne (cyanodiacetylene), HCCCCCN, is sufficiently stable at low pressures to permit its rotational spectrum to be studied by microwave spectroscopy. The spectrum consists of a series of R-branch transitions typical of a linear molecule. The transitions with J = 9 to 14 which lie between 26.5 and 40.0 GHz have been measured for the vibrational ground state. Transitions have also been detected in natural abundance for all possible singly substituted ¹³C and ¹⁵N isotopic species. Deuteriated cyanobutadiyne, DCCCCCN, has also been synthesized and its ground state spectrum recorded. These measurements have enabled a complete substitution structure to be derived for the first time for a polyacetylene: r₈(HC_a) = 1.0569 ± 0.001, r₈(C_aC_b) = 1.2087 ± 0.001, r₈(C_bC_c) = 1.3623 ± 0.003, r₈(C_cC_d) = 1.2223 ± 0.004, r₈(C_dC_e) = 1.3636 ± 0.003, $\text{r}{}_8\text{(}\text{C}{}_{\mathrm{e}}\text{}\text{N}\text{) = 1.1606 ± 0.001}\text{A}\text{?}\text{(10}{}^{\mathrm{?10}}\text{m}\text{)}$. The spectroscopic parameters for the ground state are B₀ = 1331.3313 ± 0.001 MHz and D₀ = 0.0257 ± 0.002 KHz. The dipole moment, determined from the Stark effects of the J = 9 and 10 lines, is 4.33 ± 0.03 Debye.     

Catalysed growth of novel aluminium oxide nanorods

Micron-scale coral-like aluminium oxide structures have been generated by heating a mixture of AlB₂ and Co powders in a quartz boat at ca. 1050 °C under N₂. Upon sonication in acetone, the structures break down into elongated single-crystal aluminium oxide nanorods ranging from 20 to 200 nm in diameter and up to 5 μm in length. Single Co particles are often found attached to nanorod tips. A vapour–liquid–solid (V–L–S) mechanism appears to be responsible for the aluminium oxide nanorod growth. Received: 21 January 2003 / Accepted: 22 January 2003 / Published online: 28 March 2003 RID="*" ID="*"Corresponding author. E-mail: d.walton@sussex.ac.uk     

Shock-wave resistance of WS2 nanotubes

The shock-wave resistance of WS(2) nanotubes has been studied and compared to that of carbon nanotubes. Detailed structural features of post-shock samples were investigated using HRTEM, XRD, and Raman spectroscopy. WS(2) nanotubes are capable of withstanding shear stress caused by shock waves of up to 21 GPa, although some nanotube tips and nanoparticles containing multiple structural defects in the bending regions are destroyed. Small WS(2) species, consisting of only a few layers, are extruded from the nanotubes. Well-crystallized tube bodies were found to exhibit significant stability under shock, indicating high tensile strength. XRD and Raman analyses have confirmed this structural stability. Under similar shock conditions, WS(2) tubes are more stable than carbon nanotubes, the latter being transformed into a diamond phase. WS(2) nanotubes containing small concentrations of defects possess significantly higher mechanical strength, and, as a consequence, hollow WS(2) nanoparticles are expected to act as excellent lubricants under much higher loading than was previously thought.     

The microwave spectrum,structure and dipole moment of thiocarbonyl fluoride,F2CS

The microwave spectrum of thiocarbonyl fluoride, F₂CS, has been investigated in the region 26.5–40.0 GHz. Transitions of the ¹⁹F₂¹²C₃₂S and ¹⁹F₂¹²C³⁴S isotopic species have been observed and the derived rotational constants yield the following ground stale structural parameters

The ground state rotational constants of the normal species are (in MHz)

The asymmetry parameter, x = ?0.62640, and the inertial defect Δ⁰ = 0.203 u A² which is consistent with that expected for this type of molecule, if planar.The dipole moment was determined from the Stark effect of two lines, and was found to be μ_A = 0.080 D.     

The microwave spectra of 1-cyanobut-3-ene-1-yne, CH2=CH---CC---CN and 1-cyanobut-1-ene-3-yne, HCC---CH=CH---CN

Two molecules related to cyanobutadiyne, H---CC---CC---CN, 1-cyanobut-3-ene-1-yne, CH₂=CH---CC---CN, and 1-cyanobut-1-ene-3-yne, H---CC---CH=CH---CN, have been synthesized and their microwave spectra assigned. The resulting rotational constants can be used to search for these species in the interstellar medium using radioastronomy. Interstellar information on such species will enable a better understanding of the chemistry responsible for the production of carbon chain molecules in the interstellar medium.     

Analysis of the microwave rotation spectrum of silyl cyanide,SiH3CN,in its ground and vibrationally excited states

The rotational spectrum of silyl cyanide, SiH₃CN, has been studied by microwave spectroscopy. A detailed analysis of the transitions in the excited states of the ν₃, ν₄, ν₇, and ν₈ modes has been carried out. In particular the v₈ = 1, 2, 3, and 4 vibrational satellites have been subjected to a complete vibration-rotation analysis. Ground state transitions of ²⁸SiH₃¹²C¹⁴N, ²⁹SiH₃¹²C¹⁴N, ³⁰SiH₃¹²C¹⁴N, ²⁸SiH₃¹³C¹⁴N, and ²⁸SiH₃¹²C¹⁵N have all been studied in natural abundance. The overall study has yielded a large amount of detailed vibration-rotation data. The effects of quadrupole interactions have been taken into account. To confirm the analysis, computer simulated spectra have been compared with those observed.     

The microwave spectrum of cyanohexatriyne,HCCCCCCCN

The detection of cyanobutadiyne, HC₅N, in various interstellar molecular clouds has prompted the laboratory synthesis and microwave study of the next member of the cyanopolyyne series in order to facilitate its detection by radio astronomy. In this study details of the synthesis and rotational analysis of cyanohexatriyne HC₇N are presented. The rotational constants B₀ = 564.00074 ± 0.00016 MHz and D₀ = 3.821 ± 0.087 Hz were the values used to identify HC₇N in the interstellar medium.