Molecular lines

Figure Bl.4.3. (a) A schematic illustration of the THz emission spectrum of a dense molecular cloud core at 30 K and the atmospheric transmission from ground and airborne altitudes (adapted, with pennission, from [17]). (b) The results of 345 GHz molecular line surveys of tlu-ee cores in the W3 molecular cloud the graphics at left depict tire evolutionary state of the dense cores inferred from the molecular line data [21],...

Reactions of alkenes with H-Si(l 0 0)-2 x 1 surfaces have been shown to yield films with one-dimensional (ID) molecular lines through Si-C linkages, contrary to formation of the islands observed on H-Si(l 11). The reaction can be initiated from isolated surface silyl radicals created using the tip of the STM. The STM images showed molecular lines running along and across the dimer rows depending on the chemical constituent of R in the CH2 = CH-R molecules. 

The rapid fabrication of covalently bonded ID functional molecular lines with predefined location, direction, and length provides a means to make a predesigned interconnection of molecular lines running along and across the dimer rows. Indeed, the perpendicularly connected allyl mercaptan and styrene lines or allyl mercaptan and acetone lines have been fabricated on the H-Si(l 00)-2 X 1 surface. °° 2 ... 

High resolution and high S/N spectra of 32 metal poor stars observed with various 4-m class telescopes (Israelian et al. 1998, 2001, Bihain et al. 2004) have been used to analyse N/O and C/O ratios from near-UV molecular lines of CH, NH and OH. We have carried out an independent study of the (N/O) ratio using the NH band at 3360 A and the OH lines employed by Israelian et al. (1998, 2001). Details of the analysis and stellar parameters are provided in Israelian et al. (2004). 

It is important to note that we have tried to avoid carbon-rich stars, because they have a rich molecular line spectrum, mostly CN, CH and C2, obliterating many interesting atomic lines of rare elements. This is why we had in our sample a star, CS 31082-001, in which we were able to measure the 385.97 nm line of U II, whereas in the similar r-process element enriched star CS 22892-052, but carbon rich, a CN line obliterates the U II line. 

The ab initio calculations produce values of fiy, i.e., the components of the electronically averaged dipole moment along the x y z axes defined above. In order to calculate molecular line strengths, however, we must determine, as functions of the vibrational coordinates, the dipole moment components along the molecule-fixed axes xyz (see equation (23)) defined by Eckart and Sayvetz conditions [1]. 

The purpose of this note is to call attention once more and to explain a continuous spectrum in hydrogen that has been observed by Horton and Davies and by Crew and Hulburt and others, and possessing the peculiar characteristic of occurring without the presence of either atomic or molecular lines. Horton and Davies observed that hydrogen at pressures less than 1 mm. of mercury became suffused with a blue glow when excited by electrons of less than 15 volts velocity. This glow was a continuous spectrum showing no trace of atomic or molecular lines. 

When Payne began her work in the 1920s, stellar spectroscopy was a very active area of research. Numerous elemental and molecular lines had been identified in stellar spectra. The lines observed in each star varied with the inferred temperature of the star, which was understood to mean that the elemental abundances varied with temperature. This body of data was the basis for the spectral typing of stars ( , B, A, F, G, , M, L). However, the power source for stars was not understood and it was not clear why the composition of a star should be related to its temperature. In the 1920s, it was also widely believed that the Sun had the same composition as the Earth models considered the Earth to have formed from the outer layers of the Sun. Payne used the new guantum mechanical understanding of atomic structure to show how and why the spectral lines of the different elements varied as a function of stellar spectral type. She demonstrated how the temperature of the stellar surface controls the spectral lines that are observed. Her analysis led to the conclusion that the chemical... 

Hossain, M. Z., Kato, H. S. and Kawai, M. Fabrication of interconnected ID molecular lines along and across the dimer rows on the Si(100)-(2 x 1)-H surface through the radical chain reaction. Journal of Physical Chemistry 109, 23129 (2005). 

In order to investigate the gas phase chemistry of the circumstellar envelopes around these peculiar objects, we have observed radio molecular lines of H20, SiO, HCN, and CO towards three of them BM Gem (C5, 4J), V778 Cyg (C4, 5J), and EU And (C4, 4). 

Abstract A molecular line search in the range between 85 and 89 GHz has been performed in the circumstellar envelopes of 11 evolved stars. Emissions of 29SiO J=2-l,28SiO J=2-l, HCN J=l-0, H13CN J=l-0, HC5 N J=33-32, HCO+ J=l-0 transitions and other transitions of C2 H, C4 H, and C3 N have been observed in 11 stars. We have detected the ground state 29SiO J=2-l maser in several stars. We have also detected HCN emission in VY CMa. A narrow H13CN spike feature near the central velocity has been found in the spectrum of CRL 2688. 

Here we place an upper limit to the amount of PAHs flowing out of the very well studied carbon star, IRC+10216 by placing limits on the strength of the PAH feature at 3.3 pm. Because the 3.3 pm feature is intrinsically quite broad, it is useful to consider relatively low resolution observations. Wittebom et al. (1980) have presented a spectrum with 2% resolution between 2.0 and 8.5 pm of IRC+ 10216. Treffers Cohen (1974) and Merrill Stein (1976) have presented similar data over much of the same spectral interval. Neither group detects any absorption at 3.28 pm at more than 5% of the continuum level. There is notable absorption at 3.1 pm, but this feature is believed to be a blend of sharp molecular lines (Ridgway et al. 1978). 

One of the important quantitative results that chemists are interested in and which can be derived from interstellar molecular lines is the number of molecules in a given area or volume of space. Under the condition of low optical depth (Winnewisser et al. 1979) the number of molecules contained in a column within an area F (e.g. 1 cm2) along the line of sight to the observer can be derived directly from the observed intensity of an interstellar line. This parameter, called the column density N, is related to the actual concentration n by the equation... 

The Pesticide Index (ref. 14) lists the following categories of pesticides acaricides, attractants, chemosterilants, defoliants, fungicides, herbicides, insecticides, molluscicides, nematicides, plant regulators, repellents, and rodenticides. Listings are in alphabetical order with structural and molecular formulae for single chemical entities. Other data include CAS nomenclature and number Wiswesser Line Notation LD-50 and test animal data when available physical appearance and safety information. Also provided are a CAS nomenclature index separate molecular (line) formulae of chemicals identified by their common names a separate section of Wiswesser line notations, also with common names an appendix of manufacturers, and an appendix of recent publications dealing with pesticide names. 

It is actualy possible to measure the temperature of the background radiation through the observations of the ratio of molecular lines the ratio of population on two levels for which the difference of energy is only a few Kelvin and provides a sensitive way to actually measure the temperature of the background. Such lines can be detected in the optical domain. Actually the first detection... 

P. Kruse, E. R. Johnson, G. A. DiLabio and R. A. WoLkow, Patterning of vinylferrocene on H-Si(lOO) via self-directed growth of molecular lines and STM-induced decomposition, Nano Letters 2, 807 (2002). 

Fig. 2. STM images of molecular nanostructures of styrene on H-terminated silicon surfaces resulting from reaction at single dangling bonds via the radical chain mechanism depicted in Fig. 1. This process leads to the growth of molecular lines on H/Si(100) and irregularly shaped islands on H/Si(lll).

Registry of Toxic Effects of Chemicals (Sub-)Structural Alerts Statistical Analysis System Aqueous solubility Structure-Activity Relationship Self-Consistent Field Structure Data File Sex Hormone Binding Globulin Simplified Molecular Line Entry System... 

In order to calculate a physicochemical property, the structure of a molecule must be entered in some manner into an algorithm. Chemical structure notations for input of molecules into calculation software are described in Chapter 2, Section VII and may be considered as either being a 2D string, a 2D representation of the structure, or (very occasionally) a 3D representation of the structure. Of this variety of methods, the simplicity and elegance of the 2D linear molecular representation known as the Simplified Molecular Line Entry System (SMILES) stands out. Many of the packages that calculate physicochemical descriptors use the SMILES chemical notation system, or some variant of it, as the means of structure input. The use of SMILES is well described in Chapter 2, Section VII.B, and by Weininger (1988). There is also an excellent tutorial on the use of SMILES at www.daylight.com/dayhtml/smiles/smiles-intro.html. 

Devillers et al. (1996) have commented that most QSARs for the prediction of BCF perform similarly up to log Kow 6. In view of the fact that the computer program BCFWIN version 2.14 is freely available from the EPA website (www.epa.gov/oppt/exposure/docs/episuitedl.htm), it is recommended that this be used for BCF prediction for chemicals with log < 6 the proviso is that highly reactive chemicals will probably have a higher than predicted BCF, perhaps by up to two orders of magnitude. BCFWIN requires that the chemical structure be input using Simplified Molecular Line Entry System (SMILES) notation (Weininger, 1988) or as a Chemical Abstracts Service (CAS) number. 

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