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Topic: Polyatomic molecule

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	Molecule - Wikipedia, the free encyclopedia
		A molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties.
		Molecular chemistry is concerned with the laws governing the interaction between molecules that results in the formation and breakage of chemical bonds, while molecular physics is concerned with the laws governing their structure and properties.
		Although the concept of molecule was first introduced in 1811 by Avogadro, the existence of molecules was still an open debate in the chemistry community till the work of Perrin (1911).
	en.wikipedia.org /wiki/Molecule (822 words)

	Molecule - Open Encyclopedia (Site not responding. Last check: 2007-10-14)
		In science, a molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties.
		A property of molecules is the integer ratio of the elements that constitute the compound, the empirical formula.
		Molecules have fixed equilibrium geometries--bond lengths and angles--that are dictated by the laws of quantum mechanics.
	open-encyclopedia.com /Molecules (470 words)

	Molecule - Encyclopedia.WorldSearch (Site not responding. Last check: 2007-10-14)
		A molecule consists of two or more atoms joined by shared pairs of electrons in a chemical bond.
		A substance that consists of molecules is a molecular substance or molecular compound.
		Molecules have fixed equilibrium geometries—bond lengths and angles—that are dictated by the laws of quantum mechanics.
	encyclopedia.worldsearch.com /molecule.htm (356 words)

	Molecular Orbitals - Molecular Orbitals for Polyatomic Molecules
		In general a molecular orbital in a polyatomic system extends over all the nuclei in a molecule and it is essential, if we are to understand and predict the spatial properties of the orbitals, that we make use of the symmetry properties possessed by the nuclear framework.
		Conjugated molecules are planar organic molecules consisting of a framework of carbon atoms joined in chains or rings by alternating single and double bonds.
		In the structural formulae for the cyclic molecules, e.g., benzene and naphthalene, it is usual not to label the positions of the carbon and hydrogen atoms by their symbols.
	www.chemistry.mcmaster.ca /esam/Chapter_8/section_6.html (1772 words)

	molecule -- Encyclopædia Britannica
		A receptor molecule is a special protein whose shape is complementary to a portion of a foreign molecule.
		Molecules in solution move randomly; the energy for their movement is derived from thermal energy.
		When a permeable membrane (a membrane that allows molecules to cross it) divides a heavily concentrated solution from a less-concentrated solution, there occurs a diffusion of molecules through the membrane and down their concentration gradient—that is, from the fluid with...
	www.britannica.com /eb/article?tocId=9053247 (879 words)

	molecule -- Britannica Concise Encyclopedia Online Article
		For noble gases, the molecule is a single atom; all other substances have two (diatomic) or more (polyatomic) atoms in a molecule.
		Molecules of different substances can have the same constituent atoms, either in different proportions, as in carbon monoxide (CO) and carbon dioxide (CO), or bonded in different ways (see isomer).
		(The concept of molecules has no significance in solids with ionic bonds.) Analysis with modern techniques and computers can determine and display the size, shape, and configuration of molecules, the positions of their nuclei and electron clouds, the lengths and angles of their bonds, and other details.
	www.britannica.com /ebc/article?tocId=9372411 (1012 words)

	interstellar molecule Comparison Table (Site not responding. Last check: 2007-10-14)
		A molecule consisting of one carbon atom and one oxygen atom.
		It is the most abundant interstellar molecule after molecular hydrogen and is especially useful because it radiates at radio wavelengths, so astronomers can use it to map the distribution of molecular hydrogen.
		A molecule discovered in interstellar apace in 1974, in Sgr B2, at a frequency of 87.77 GHz.
	www.site.uottawa.ca:4321 /astronomy/interstellarmolecule_table.html (301 words)

	Molecule
		Fuel molecule A fuel molecule is a molecule metabolized by a cell to generate ATP.
		Molecule A molecule is an electrically neutral cluster of two or more atoms joined by shared pairs of electrons (covalen...
		Odd molecule Odd molecule is a term invented by Nitrogen dioxide is another.
	www.brainyencyclopedia.com /topics/molecule.html (105 words)

	[No title]
		An example of a property of a molecule that is sensitive to molecular structure is polarity of the molecule.
		Molecules can be either polar (have a dipole) or non-polar (do not have a dipole).
		Whether a molecule has a dipole or no dipole can be determined from the molecular structure of the molecule.
	www.baruch.cuny.edu /wsas/departments/natural_science/chemistry/chm_1000/molec_mod.doc (393 words)

	List of Participants
		Understanding the dynamics of molecules at energies where chemical bonds break or are formed is not only of academic importance but basically it is the foundation of chemistry with all the consequences that implies for our continuously advancing technological world.
		Numerous studies show that the polyatomic molecules seen as a set of non-linear coupled oscillators is not an ergodic system, but instead, they form a mixed phase space with regular and chaotic regions [4,5].
		Systematic studies mainly in triatomic molecules have shown that the route to a bond breaking or formation with the increase of energy is paved by a cascade of such bifurcations [4,5].
	tccc.iesl.forth.gr /cecam2004/specr_compch.html (1402 words)

	NIST: Triatomic - Molecular Param. and Energy Level Form
		The treatment of the rotational energy levels and transition frequencies for polyatomic molecules is more complicated than the formulations applied to diatomic molecules [2].
		These three classes, linear molecules, non-linear molecules, and molecules having doublet (or multiplet) ground electronic states, will be described separately and in that order, since each successive type shows increasingly complex interactions through their rotational spectra.
		In spite of the fact that triatomic molecules are the simplest polyatomic species, a thorough discussion of the theoretical background of their rotational spectra and energy level interactions would entail an extensive text in itself, and would require repetition of many excellent treatments readily available.
	physics.nist.gov /PhysRefData/MolSpec/Triatomic/Html/sec2.html (1696 words)

	Rotational Spectra of Rigid Rotor Molecules
		The spectra for rotational transitions of molecules is typically in the microwave region of the electromagnetic spectrum.
		For a diatomic molecule the rotational energy is obtained from the Schrodinger equation with the Hamiltonian expressed in terms of the angular momentum operator.
		The rotational spectrum of a diatomic molecule consists of a series of equally spaced absorption lines, typically in the microwave region of the electromagnetic spectrum.
	hyperphysics.phy-astr.gsu.edu /hbase/molecule/rotrig.html (398 words)

	Geom03 (Site not responding. Last check: 2007-10-14)
		The molecule can be oriented such that one end has a net negative charge and the other a net positive charge, i.e.
		Although a polar bond is a prerequisite for a molecule to have a dipole, not all molecules with polar bonds exhibit dipoles
		For ABn molecules, where the central atom A is surrounded by identical atoms for B, there a certain molecular geometries which result in no effective dipole, regardless of how polar the individual bonds may be.
	wine1.sb.fsu.edu /chm1045/notes/Geometry/Polarity/Geom03.htm (361 words)

	Molecular Structure from Rotational Spectra
		The most accurate way to determine the molecular structure of a molecule in the gas phase is by analysis of the rotational spectrum.
		The structure of a diatomic molecule has only one unknown, but when you have multiple bond lengths and angles, you have several unknowns and need several equations to solve for them.
		The molecule is quite unstable and explosive on contact with air, so we treated the deuterated sample with great care and took data on its spectrum for about two weeks.
	hyperphysics.phy-astr.gsu.edu /hbase/molecule/spf2h.html (753 words)

	Molecular Geometry and Electron Domain Theory (Site not responding. Last check: 2007-10-14)
		However, with a triatomic molecule (three atoms), there are two possible geometries: the atoms may lie on a line, producing a linear molecule, or not, producing a bent molecule.
		In molecules in crystalline form, the geometry of the molecule is revealed by irradiating the crystal with x-rays and analyzing the patterns formed as the x-rays diffract off of the crystal.)
		The Cl-X-Cl bond angles in the two molecules are identical, because the bond angle is determined by the repulsion of the two Cl atoms, which is identical in the two molecules.
	cnx.rice.edu /content/m12594/latest (3584 words)

	Molecular Orbitals for Polyatomic Molecules
		The molecular orbitals in the water molecule are classified as a1, b1 or b2 orbitals, as determined by their symmetry properties.
		Aside from the presence of the second proton, the general form and nodal structure of the 2a1 density distribution in the water molecule is remarkably similar to the 2s distributions in CH and HF, and particularly to the latter.
		The charge density accumulated on the bonded side of the oxygen nucleus in the 2a1 orbital is localized near this nucleus as the corresponding charge increase in the 2s orbital of HF is localized near the fluorine.
	www.cartage.org.lb /en/themes/Sciences/Physics/MolecularPhysics/MolecularSpectra/Polyatomic/Polyatomic.htm (2038 words)

	Nat' Academies Press, Biographical Memoirs V.56 (1987)
		This they found in the molecule of hexene, anti they were able to show a small depletion of the number of molecules in the ortho form of the iodine molecule by this photochemical reaction.
		Recognizing the importance of regularities in behavior from molecule to molecule in unclerstancling the nature of the chemical bond, and giving consideration to the earlier attempts to express these analytically, Badger carried out an extensive survey of the information available on the force constant and internuclear distance in a considerable number of diatomic molecules.
		Uncertainties regarding the structure of the isothiocyanic acid molecule led Badger, with one of his students, to record a portion of the infrared spectrum of isothiocyanic acid va- por, an analysis of which contributed importantly to an unclerstancTing of the structure of this molecule.
	www.nap.edu /books/0309036933/html/1.html (3952 words)

	General Chemistry Online: Glossary: Simple compounds
		a molecule or ion that donates an electron pair to form a chemical bond.
		All of the noninert gases occur as diatomic molecules; e.
		O (copper sulfate pentahydrate) are made of regularly repeating units, each containing 5 molecules of water weakly bound to a copper(II) ion and a sulfate ion.
	antoine.frostburg.edu /chem/senese/101/compounds/glossary.shtml (1360 words)

	AUTHOR: Benjamin, I
		A30229 of 1973) is applied to the case of a diatomic molecule, and the case of relaxation of a polyatomic molecule at its lowest vibrational frequency.
		For a diatomic molecule and for a small polyatomic the molecular eigenstates are excited by a coherent multiphoton excitation process, while for large polyatomic molecules where the low electronically excited state corresponds to an intermediate level structure or to the statistical limit, incoherent multiphoton excitation of the molecular eigenstates of an 'isolated' molecule prevails.
		For a cluster of N molecules the light-scattering cross section is made of two contributions: a coherent part (proportional to N/sup 2/) which may be described by the dielectric-function concept and an incoherent part (proportional to N).
	atto.tau.ac.il /~nitzan/abstracts.html (12452 words)

	Normal modes
		Molecules also rotate but the rotational motion is slow compared to the vibration.
		Further more, in a symmetric polyatomic molecule like carbon dioxide only the asymmetric vibrations that create a dipole will be infrared-active.
		A normal mode is a collective motion of all the atoms in the molecule where each atom in the molecule moves in phase with each other at a particular frequency.
	cat.middlebury.edu /~chem/chemistry/ch2cl2 (1668 words)

	Dipole moments of polyatomic molecules (Site not responding. Last check: 2007-10-14)
		The total dipole of a polyatomic molecule can be determined directly from the formula for the dipole moment of an assembly of charges.
		Thus, the total dipole moment is given by the sum of the dipole moments of the individual OH bonds in the molecule.
		The total dipole moment of the water molecule is not zero, a fact that leads to some interesting properties of liquid water and ice.
	nyu.edu /classes/tuckerman/honors.chem/lectures/lecture_7/node7.html (119 words)

	Polyatomic molecule
		Polyatomic molecules are molecules in chemistry that consist only of atoms of a single element.
		These are the most widely accepted polyatomic molecules:
		The text of this article is licensed under the GFDL.
	www.ebroadcast.com.au /lookup/encyclopedia/po/Polyatomic_molecule.html (199 words)

	PHS702 Statistical Thermodynamics, Lecture 7
		We have 3N - 6 degrees of vibrational freedom (3N - 5 for a linear molecule) in polyatomic molecules.
		The rotational energies of the non-linear rigid body depends on the symmetry in terms of the rotational constants of the molecule.
		When nearly free rotation of a group is present in a molecule, the molecular partition function has to be modified.
	phoenix.liu.edu /~nmatsuna/PHS702/statmech/lect7/stat.mech.8.html (558 words)

	8.3 Vibration
		For diatomic molecules two additional ones are rotational, one about the x-axis and one about the y-axis and none about the z (bond) axis.
		So for a diatomic molecule there are six motional degrees of freedom, three translational, two rotational, and hence only one vibrational.
		For any non-linear polyatomic molecule of n atoms, there are 3n motional degrees of freedom.
	scholar.chem.nyu.edu /0652/notes/stat/node15.html (463 words)

	FUNDAMENTAL CHALLENGES IN ELECTRON-DRIVEN CHEMISTRY
		While there have been remarkable calculations for a number of diatomic and a few polyatomic molecules that treated this problem with varying levels of success, they have in general not taken advantage of many of the developments in bound-state quantum chemistry of the past fifteen years.
		The range of molecules that can be treated will grow dramatically over the next several years as computer technology transitions to the teraflops capabilities of tomorrow and to the petaflops capabilities of the not-so-distant future.
		Electronic collisions with polyatomic molecules are of fundamental theoretical importance in this context, because with many vibrational degrees of freedom and opportunities for interaction between excited electronic states, they offer a rich array of nonadiabatic processes which are still not completely understood.
	www.lbl.gov /ICSD/mccurdy/workshop_final_1.html (9124 words)

	IVR in polyatomic molecules
		The study of highly excited polyatomic molecules is interesting because of phenomena as Statistical Intramolecular Vibrational-energy Redistribution (IVR).
		In a typical experiment, a photon absorbed by the molecule leads it into some nonstationary state (initial or bright state) with a sizable dipole matrix element to the ground state.
		Here follows a sample spectrum of the water molecule (the bright state (1,0,0) has 1 quantum of the symmetric OH stretching mode), for which ab-initio frequencies and anharmonic coupling are available in the literature [A.G.Csaszar and I.M.Mills, Spectrochim.
	www.mi.infm.it /manini/ivr.html (709 words)

	Sampling of semiclassically quantized polyatomic molecule vibrations by an adiabatic switching method: Application to ... (Site not responding. Last check: 2007-10-14)
		Sampling of semiclassically quantized polyatomic molecule vibrations by an adiabatic switching method: Application to quasiclassical trajectory calculations
		We apply the adiabatic switching (AS) method to determine the polyatomic classical motions that correspond to selected vibrational quantum states on multidimensional, anharmonic potential energy surfaces, and use these semiclassically quantized motions as initial conditions for quasiclassical trajectory (QCT)calculations of state-to-state reaction dynamics.
		QCT calculations of state-to-state dynamics using CD with no ZPE, the ZPE from AS sampling, and the ZPE from normal-mode sampling are reported and compared.
	www.chemistry.bnl.gov /GPMD/old-pages/MUCKAB5.HTML (298 words)

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