12C 14N Research Articles

TH-C-BRD-01: Analytical Computation of Prompt Gamma Ray Emission and Detection for Proton Range Verification

Purpose: A prompt gamma (PG) slit camera prototype demonstrated that on-line range monitoring within 1–2 mm could be performed by comparing expected and measured PG detection profiles. Monte Carlo (MC) can simulate the expected PG profile but this would result in prohibitive computation time for a complete pencil beam treatment plan. We implemented a much faster method that is based on analytical processing of pre-computed MC data. Methods: The formation of the PG detection signal can be separated into: 1) production of PGs and 2) detection by the camera detectors after PG transport in geometry. For proton energies from 40 to 230 MeV PG productions in depth were pre-computed by MC (PENH) for 12C 14N 16O 31P and 40Ca. The PG production was then modeled analytically by adding the PG production for each element according to local proton energy and tissue composition.PG transport in the patient/camera geometries and the detector response were modeled by convolving the PG production profile with a transfer function. The latter is interpolated from a database of transfer functions fitted to pre-computed MC data (PENELOPE). The database was generated for a photon source in a cylindrical phantom with various radiuses and a camera placed at various positions.As a benchmark the analytical model was compared to PENH for a water phantom a phantom with different slabs (adipose muscle lung) and a thoracic CT. Results: Good agreement (within 5%) was observed between the analytical model and PENH for the PG production. Similar accuracy for detecting range shifts was also observed. Speed of around 250 ms per profile was achieved (single CPU) using a non-optimized MatLab implementation. Conclusion: We devised a fast analytical model for generating PG detection profiles. In the test cases considered in this study similar accuracy than MC was achieved for detecting range shifts.

Determination of the nitrogen abundance in organic materials by NanoSIMS quantitative imaging

We describe a procedure to determine precise and accurate elemental abundance by means of quantitative imaging using secondary ion mass spectrometry (on images covering ∼10 × 10 μm2) applied to natural Insoluble Organic Matter (IOM). Dynamic SIMS conditions are reached for a 16 keV Cs+ fluence of >2.0 × 1017 Cs+ cm−2 implanted at the surface of the IOM. Once the sample surface is saturated in cesium, steady-state implantation and sputtering yield are reached: constant secondary ion count rates are then observed. Two calibrations of the nitrogen abundance are presented. The nitrogen abundance is expressed either as [N] or N/C atomic ratio calibrated by means of 12C14N−/12C− or 12C14N−/12C2− ionic ratios respectively. The 12C14N−/12C− uncertainty is always larger than the uncertainty of 12C14N−/12C2−. At a smaller scale inside an image (∼1 × 1 μm2), a little larger than the primary beam size, processes induced by topographic irregularity of the IOM powder result in a variation of the 12C14N−,12C2− and 12C− count rates and increase the variability of the ionic ratios. The chemical contrast produced by a rough sample surface exposed to the Cs+ rastering is evaluated with a scratched epoxy resin for 12C14N−/12C− and 12C14N−/12C2− elemental ratios. Owing to similarities in emission parameters, the determination of the N/C ratio in rough organic surfaces is improved by using 12C 14N−/12C2− instead of 12C 14N−/12C−.

Spectroscopic parameter and molecular constant investigations on X 2Σ + and A 2Π i states of 12C 14N, 12C 15N, 13C 14N and 13C 15N species

The potential energy curves of X 2Σ + and A 2Π i states of CN radical have been investigated using the complete active space self-consistent-field method followed by the highly accurate valence internally contracted multireference configuration interaction approach in combination with the cc-pV5Z basis set. With the second-order Douglas–Kroll Hamiltonian approximation, the effect on the PECs by the relativistic corrections has been taken into considerations. Employing the cc-pcV5Z basis set, the effect on the spectroscopic parameters by the core-correlate corrections has been evaluated. For the X 2Σ + and A 2Π i electronic states, the spectroscopic parameters of these four species ( 12C 14N, 13C 14N, 12C 15N and 13C 15N) have been studied. With the CN potential energy curves obtained here, 43 vibrational states for the X 2Σ + and 60 for the A 2Π i states are predicted when the rotational quantum number J is equal to zero ( J = 0). The vibrational manifolds are determined for the first 40 vibrational states when J = 0. And the rovibrational energy levels of four species are calculated until J = 29. The results of spectroscopic parameters and molecular constants have been compared in detail with those of the investigations reported in the literature.

Dynamic SIMS ion microscopy imaging of individual bacterial cells for studies of isotopically labeled molecules

A CAMECA IMS-3f SIMS ion microscope instrument capable of 500 nm spatial resolution was used for imaging single bacterial cells in the soil treated with 13C-labeled phenol in desired treatments. After formaldehyde fixation, the soil samples containing bacterial cells were smeared on the silicon substrate. The O 2 + primary ion beam was used for the detection of negative secondary ions. Images of individual bacterial cells were recorded on a CCD camera in masses 24, 25, 26, and 27 signals. The respective mass images represented contributions from the molecular ions of interest, for example 24( 12C 2) −, 25( 13C 12C) −, 26( 12C 14N) −, 27( 13C 14N) −, as well as interfering mass species associated with a particular mass. However, in cells treated with 13C-labeled phenol the enhancement of signals in masses 25 and 27 images due to increased signals of 25( 13C 12C) − and 27( 13C 14N) −, respectively, unequivocally indicated the presence of 13C-labeled phenol in bacterial cells in direct comparison to the samples treated only with unlabeled phenol. The ratio images of masses 25/24 and 27/26 from individual cells revealed a cell-to-cell heterogeneity in the labeling with 13C-phenol. This study indicates that the ion microscope can be applied effectively for studies of labeled molecules in microbiology and biogeochemistry.

Low-temperature measurements of HCN broadened by N 2 in the 14-μm spectral region

Half-width and pressure-induced shift coefficients; the temperature-dependence exponents of the half-widths and the temperature-dependence coefficients of pressure-induced shifts have been measured for N 2-broadened transitions in the ν 2 band of HCN. Line positions and intensities were also determined. A total of 34 laboratory absorption spectra, recorded at 0.002–0.005 cm −1 resolution with two different Fourier transform spectrometers, were used in the determination of the spectral line parameters. The total pressures of the HCN–N 2 samples ranged from less than 1 torr up to nearly 1 atm, and temperatures were between 211 and 300 K. A multispectrum nonlinear least-squares fitting technique employing a modified Voigt line profile, including speed dependence and line mixing via the off-diagonal relaxation matrix formulation, was used in the analysis. Speed-dependence parameters were determined in the P and R branches of the ν 2 band of H 12C 14N, and in the ν 2 Q branches of H 12C 14N and H 13C 14N the off-diagonal relaxation matrix elements that characterize line mixing were included in the analysis to fit the data. Present results are compared with previous measurements reported in the literature.

The Titan 14N/ 15N and 12C/ 13C isotopic ratios in HCN from Cassini/CIRS

We report the detection of H 13CN and HC 15N in mid-infrared spectra recorded by the Composite Infrared Spectrometer (CIRS) aboard Cassini, along with the determination of the 12C/ 13C and 14N/ 15N isotopic ratios. We analyzed two sets of limb spectra recorded near 13–15° S (Tb flyby) and 83° N (T4 flyby) at 0.5 cm −1 resolution. The spectral range 1210–1310 cm −1 was used to retrieve the temperature profile in the range 145–490 km at 13° S and 165–300 km at 83° N. These two temperature profiles were then incorporated in the atmospheric model to retrieve the abundance profile of H 12C 14N, H 13CN and HC 15N from their bands at 713, 706 and 711 cm −1, respectively. The HCN abundance profile was retrieved in the range 90–460 km at 15° S and 165–305 km at 83° N. There is no evidence for vertical variations of the isotopic ratios. Constraining the isotopic abundance profiles to be proportional to the HCN one, we find C 12 / C 13 = 89 −18 +22 at 15° S, and 68 −12 +16 at 83° N, two values that are statistically consistent. A combination of these results yields a 12C/ 13C value equal to 75 ± 12 . This global result, as well as the 15° S one, envelop the value in Titan's methane ( 82.3 ± 1 ) [Niemann, H.B., and 17 colleagues, 2005. Nature 438, 779–784] measured at 10° S and is slightly lower than the terrestrial inorganic standard value (89). The 14N/ 15N isotopic ratio is found equal to 56 −13 +16 at 15° S and 56 −9 +10 at 83° N. Combining the two values yields 14N/ 15N = 56 ± 8, which corresponds to an enrichment in 15N of about 4.9 compared with the terrestrial ratio. These results agree with the values obtained from previous ground-based millimeter observations [Hidayat, T., Marten, A., Bézard, B., Gautier, D., Owen, T., Matthews, H.E., Paubert, G., 1997. Icarus 126, 170–182; Marten, A., Hidayat, T., Biraud, Y., Moreno, R., 2002. Icarus 158, 532–544]. The 15N/ 14N ratio found in HCN is ∼3 times higher than in N 2 [Niemann, H.B., and 17 colleagues, 2005. Nature 438, 779–784], which implies a large fractionation process in the HCN photochemistry.

Sub-cellular localisation of a 15N-labelled peptide vector using NanoSIMS imaging

Dynamic SIMS imaging is proposed to map sub-cellular distributions of isotopically labelled, exogenous compounds. NanoSIMS imaging allows the characterisation of the intracellular transport pathways of exogenous molecules, including peptide vectors employed in innovative therapies, using stable isotopes as molecular markers to detect the compound of interest. Shiga toxin B-subunit (STxB) was chosen as a representative peptide vector. The recombinant protein ( 15N-STxB) was synthesised in Escherichia coli using 15NH 4Cl as sole nitrogen source resulting in 15N enrichment in the molecule. Using the NanoSIMS 50 ion microprobe (Cameca), different ion species ( 12C 14N −, 12C 15N −, 31P −) originating from the same sputtered micro volume were simultaneously detected. High mass resolving power enabled the discrimination of 12C 15N − from its polyatomic isobars of mass 27. We imaged the membrane binding and internalisation of 15N-STxB in HeLa cells at spatial resolutions of less than 100 nm. Thus, the use of rare stable isotopes like 15N with dynamic SIMS imaging permits sub-cellular detection of isotopically labelled, exogenous molecules and imaging of their transport pathways at high mass and spatial resolution. Application of stable isotopes as markers can replace the large and chemically complex tags used for fluorescence microscopy, without altering the chemical and physical properties of the molecule.

Supported Membrane Composition Analysis by Secondary Ion Mass Spectrometry with High Lateral Resolution

The lateral organization of lipid components within membranes is usually investigated with fluorescence microscopy, which, though highly sensitive, introduces bulky fluorophores that might alter the behavior of the components they label. Secondary ion mass spectroscopy performed with a NanoSIMS 50 instrument also provides high lateral resolution and sensitivity, and many species can be observed in parallel without the use of bulky labels. A tightly focused beam (∼100 nm) of Cs ions is scanned across a sample, and up to five of the resulting small negative secondary ions can be simultaneously analyzed by a high-resolution mass spectrometer. Thin layers of 15N- and 19F-labeled proteins were microcontact-printed on an oxidized silicon substrate and imaged using the NanoSIMS 50, demonstrating the sensitivity and selectivity of this approach. Supported lipid bilayers were assembled on an oxidized silicon substrate, then flash-frozen and freeze-dried to preserve their lateral organization. Lipid bilayers were analyzed with the NanoSIMS 50, where the identity of each specific lipid was determined through detection of its unique secondary ions, including 12C 1H −, 12C 2H −, 13C −, 12C 14N −, and 12C 15N −. Steps toward obtaining quantitative composition analysis of lipid membranes that varied spatially in isotopic composition are presented. This approach has the potential to provide a composition-specific analysis of membrane organization that compliments other imaging modalities.

A multispectrum analysis of the ν2 band of H 12C 14N: Part II. Theoretical calculations of self-broadening, self-induced shifts, and their temperature dependences

A semiclassical theory based upon the Robert–Bonamy formalism has been developed to explain the experimental measurements of self-broadening, self-induced pressure shift coefficients in the ν 1, ν 2, 2 ν 2 bands of H 12C 14N and the 2 ν 1 band of H 13C 14N, as well as the temperature dependences of these parameters with special emphasis on the ν 2 band. Our calculations include only electrostatic interactions and neglect the vibrational dependence of the isotropic part of the intermolecular potential, which probably has a weak contribution to the HCN self-shifts for the bands investigated in this study. The agreement between theory and measurements is good in the cases of self-broadening coefficients and their variation with temperature, as well as the self-shift coefficients determined at room temperature. However, the observed temperature dependence of self-shift coefficients in the ν 2 band is different from that derived theoretically.

A multispectrum analysis of the 2 ν2 spectral region of H 12C 14N: intensities, broadening and pressure-shift coefficients

High-resolution (0.005 cm −1) infrared absorption spectra of HCN in the 2 ν 2 band region near 1411 cm −1 have been recorded at room temperature using the Bruker IFS120HR Fourier transform spectrometer located at Pacific Northwest National Laboratory. Four spectra of high-purity (99.8%) HCN together with three spectra of lean mixtures (∼3%) of HCN in dry air were simultaneously fit using a multispectrum nonlinear least-squares procedure. The analysis yielded room temperature values for absolute intensities, self- and air-broadening coefficients, and self- and air-induced pressure shift coefficients for numerous lines in the 2 ν 2 0 band of H 12C 14N. In addition, intensities, self- and air-broadening coefficients for several lines of the 3 ν 2 1− ν 2 1 hot band, as well as intensities for a number of lines in the 2 ν 2 0 band of H 13C 14N, were also determined. Since there are no previous measurements of broadening and shift parameters reported in the 2 ν 2 0 band, our results are compared with values recently determined in the ν 1 band of H 12C 14N and with current HITRAN values.

Fourier transform infrared spectroscopy of the 2 ν3 overtone band of different ICN isotopomers: an improved evaluation of the anharmonic force field of cyanogen iodide

The weak 2 ν 3 overtone band of the three isotopomers of cyanogen iodide, I 12C 14N, I 13C 14N, and I 12C 15N, has been recorded in the range from 4200 to 4400 cm −1 with a resolution of 0.02 cm −1 using a Fourier transform infrared spectrometer. The following band origins have been determined from the analysis of the spectra: ν 0 (I 12C 14N)=4332.8368 cm −1, ν 0 (I 13C 14N)=4235.7355 cm −1, and ν 0 (I 12C 15N)=4274.2851 cm −1. This allowed us to achieve complete knowledge of the energies for all levels of ICN corresponding to double vibrational excitation. An improved evaluation of the quartic force field of cyanogen iodide has been performed using the new data obtained together with those already known from previous works.

A multispectrum analysis of the ν1 band of H 12C 14N: Part I. Intensities, self-broadening and self-shift coefficients

The infrared spectrum of HCN in the region between 3150 and 3450 cm −1 has been recorded at 0.005 and 0.008 cm −1 resolution using two different Fourier transform spectrometers, the McMath–Pierce Fourier transform spectrometer located at the National Solar Observatory (on Kitt Peak) and the Bruker-120HR Fourier transform spectrometer situated at the Pacific Northwest National Laboratory at Richland, Washington. Room temperature measurements were made of positions, absolute intensities, self-broadening and self-shift coefficients for individual lines belonging to the HCN ν 1 band centered near 3311 cm −1 . These are to our knowledge the first extensive set of self-broadening and self shift measurements in the band. In addition, intensities, self-broadening and self-shift coefficients for several lines of the ν 1+ ν 2 1− ν 2 1 hot band and several intensities for lines in the H 13C 14N and H 12C 15N isotopomers were also determined. A multispectrum nonlinear least-squares fitting algorithm was used to fit the entire spectral region covering the 3200– 3400 cm −1 region of up to 27 spectra simultaneously. The measured line intensities in the ν 1 band were further analyzed to derive the vibrational band intensity and the Herman–Wallis coefficients. Differences in line intensities between 5 and 10% are found with respect to present measurements and the values given in the HITRAN database for m values beyond 25 in the P branch and 5 in the R branch.

A multispectrum analysis of the ν1 band of H 12C 14N: Part II. Air- and N 2-broadening, shifts and their temperature dependences

Air- and N 2-broadening, air- and N 2-pressure-induced shift coefficients and the temperature dependence exponent of the broadening coefficients and the temperature dependent coefficient of pressure-induced shifts have been determined for transitions of the ν 1 band of H 12C 14N from 39 laboratory absorption spectra recorded at 0.005 and 0.008 cm −1 resolutions with two different Fourier transform spectrometers. The parameters were retrieved from the multispectrum nonlinear least-squares fits to the 3200– 3400 cm −1 region of spectra recorded at temperatures between +26°C and −60°C. Pure samples of HCN in a 19.95 cell and a 0.958 cm cell at room temperature as well as lean mixtures of HCN in N 2 or dry air in a coolable cell with a 50 cm absorption path were used in the experiments. Line parameters for N 2 broadening were determined by fitting 27 spectra simultaneously while air-broadening parameters were quantified from simultaneous fits to 22 spectra. The average ratio and the standard deviation of the room-temperature air- to N 2-broadening coefficient of lines with assignments between P(29) and R(28) are 0.904±0.001. Pressure-induced shift coefficients at 296 K are all negative with values between 0 and ∼−0.006 cm −1 atm −1 and different rotational dependences in the P- and R-branches. Differences between our results, previous measurements and the parameters that are reported in the 2000 edition of HITRAN (HIgh-resolution TRANsmission) database are quantified and discussed.

An improved evaluation of the equilibrium structure of cyanogen iodide

The millimetre-wave spectra of I 12C 14N in the 10 00, 02 00 and 02 20 vibrational states were measured. A more precise equilibrium rotational constant was calculated and a new evaluation of the equilibrium structure of cyanogen iodide was made by using the B e values of three different isotopomers. The following results were obtained: r e ( CI) = 1.99202 ± 0.00006 A ̊ and r e ( CN) = 1.16055 ± 0.00009 A ̊ . The ground-state millimetre-wave spectrum of I 13C 15N was also recorded, and the substitution structure of cyanogen iodide was calculated from four different parent molecules.

A Fermi resonance study in H 12C 14NH 19F based on gas phase far infrared spectroscopy

A static gas phase far infrared spectroscopic investigation of seven hot bands involving the intermolecular bend ν 1 7 in the hydrogen-bonded species HCN-HF has been performed. The information obtained from a rovibrational analysis of these hot bands is combined with previously available microwave and infrared spectroscopic data to reinvestigate Fermi resonance interactions of 2 ν 0 7 with ν 4 and 3 ν 1 7 with ν 4 + ν 1 7. Corresponding Fermi resonance shifts of 2.31(5) cm −1 and 3.04(9) cm −1 were calculated respectively. Anharmonic constants x 77 = − 1.228(3) cm −1 and g 77 = 1.136(3) cm −1 were also determined and compared with values of value of x 77 = − 2.29 cm −1 and g 77 = 1.06 cm −1 evaluated by Amos [R.D. Amos, J.F. Gaw, N.C. Handy, E.D. Simandiras and K. Somasundram, Theoret. Chim. Acta, 71 (1987) 41] from an ab initio calculation.

Hydrogen cyanide: theory and experiment

The results of large-scale ab initio calculations for hydrogen cyanide are compared with available experimental data. The equilibrium bond lengths of the electronic ground state are obtained with an accuracy of ≈ 0.0005 Å and the wavenumbers of the fundamental vibrational transitions have errors of 2.1 cm −1 ( ν 1), 1.3 cm −1 ( ν 2) and 5.8 cm −1 ( ν 3). An accurate three-dimensional CCSD(T) electric dipole moment is reported and, by combination of experiment and theory, the equilibrium dipole moment is determined as being μ e = − 3.0146(5) D. The calculated transition dipole moments of the ν 3 bands of HCN isotopomers agree with experiment, and the intensity anomaly found experimentally for H 12C 14N and H 12C 15N is reproduced by theory for the first time. Accurate equilibrium geometries are reported for the two lowest electronic states of HCN + (X̃ 2Π and A ̃ 2Σ + ). By combination of experimental and theoretical data, the equilibrium excitation energy of the first excited singlet state (Ã 1 A″) is obtained as T e = 53 266 ± 30 cm −1. The equilibrium geometry of the lowest triplet state (ã 3A′) is r e = 1.100 A ̊ , R e = 1.288 A ̊ and α e = 120.9 °. Its T e value is recommended as being 38 500 ± 500 cm −1.

Formation of aminomethylidyne from hydrogen cyanide on Pt(111)

The thermal chemistry of HCN has been investigated from 85 to 450 K by Fourier transform-infrared absorption spectroscopy (FT-IRAS) and thermal desorption spectroscopy (TDS). The adsorption of HCN at 85 K yields an infrared spectrum consisting of an intense band at 3298 cm −1 due to the CH stretch and a weak band at 1311 cm −1 that is assigned to the overtone of the HCN bend. The close resemblance between the IR spectrum of HCN absorbed on Pt(111) at 85 K and the IR spectrum of HCN in the gas phase and trapped in an argon matrix suggests that HCN is adsorbed molecularly at 85 K and is only weakly perturbed by the surface. Upon warming to 300 K, the H 12C 14N is transformed to a new molecular species with bands at 3363, 1567, and 1323 cm −1. From the shifts of these bands following initial adsorption of the H 13C 14N and H 12C 15N isotopes, they are assigned to an NH stretch (3363 cm −1), NH 2 bend (1567 cm −1), and CN stretch (1323 cm −1). Comparison with the IR spectrum of an Os 3H(μ-CNH 2)CO 10 complex indicates that the 300 K species is aminomethylidyne, CNH 2.

Fourier Transform Spectra of Overtone Bands of HCN from 4800 to 9600 cm −1: Some New Transitions of Bending Combination Modes

The transition moments and vibration-rotation constants of 18 previously unobserved combination and/or hot bands of H 12C 14N are reported. Overtone absorption spectra were measured with a Fourier transform interferometer and a multipass absorption cell with a pathlength of up to 352 m. The transition wavenumber measurements were used to derive vibration-rotation constants, and the integrated line intensities were used to derive an estimate of the transition moments. The new transitions are 01 13-01 10, 11 12-00 00, 12 02-000, 32 00-02 00, 32 20-02 20, 03 12-01 10, 03 12-00 00, 13 11-01 10, 13 11-00 00, 13 31-02 20, 23 30-03 30, 23 10-03 10, 23 10-00 00, 03 12-02 00, 03 32-02 20, 14 01-02 00, 14 21-02 20, and 04 02-00 00.

Stable multi-line CW vibration laser near 5 μm based on F H(CN −) centers in CsBr

Stable cw laser operation has been obtained from F center/CN - defect pairs, “F H(CH -) centers”, in CsBr crystals. Pumped with the 676 nm krypton laser line in one of their electronic absorption transitions in the visible, the F H(CN -) centers perform (e-v) energy transfer into higher vibrational (v) levels of the CN - molecule and lase on their v=3→2 CN - vibrational transition near 5 μm up to a crystal temperature limit of ≈30 K. Using F H(CN -) defects with 12C 14N, 12C 15N, 13C 14N and 13 C 15N isotopes in the same crystal, we could obtain simultaneous four-line laser operation at 2010, 1980, 1970 and 1940 cm −1.

Fourier transform spectra of overtone bands of HCN from 5400 to 15100 cm −1

The absolute intensities and vibration-rotation constants of 26 overtone and combination bands of HCN are reported. The dynamic range for the absolute intensity measurements is nearly one million to one. Absorption spectra of HCN from 5400 to 15100 cm −1 were obtained using the Fourier transform spectrometer at the Kitt Peak National Solar Observatory with optical path lengths up to 432 m. The frequencies of 1346 assigned HCN lines were used to derive vibration-rotation constants for 23 bands (14 Σ-Σ, 4 Π-Π, 4 Π-Σ, and 1 Σ-Π) of H 12C 14N, 3 bands (Σ-Σ) of H 13C 14N, and 2 bands (Σ-Σ) of H 12C 15N. These new band origin and rotational constant data have been combined with existing data given in the literature to derive an improved set of vibrational (ω, x, and y) constants and rovibrational (α and γ) constants for HCN. The vibrational dependence of the centrifugal distortion constants has also been examined. One thousand thirtysix derived line areas were used to determine absolute intensities for all 28 bands. Four weak stretch-only bands were observed for the first time: the (300)-(000), the (201)-(000), the (301)-(000) and the (202)-(000). Such data should be an important aid in accurately determining the CN contribution to the potential and dipole moment functions. Finally, we present a comparison of 13 of the measured absolute overtone intensities (stretching states only) with recent ab initio results.