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Context. Wide-field spectrometers are needed to deal with current astrophysical challenges that require multiband observations at millimeter wavelengths. An example of these is the KIDs Interferometer Spectrum Survey (KISS), which uses two arrays of kinetic inductance detectors (KIDs) coupled to a Martin-Puplett interferometer (MPI). KISS has a wide instantaneous field of view (1 deg in diameter) and a spectral resolution up to 1.45 GHz in the 120-180 GHz electromagnetic band. The instrument is installed on the 2.25 m Q-U-I JOint TEnerife telescope in Teide Observatory (Tenerife, Canary Islands), at an altitude of 2395 m above sea level. Aims. This work presents an original readout modulation method developed to improve the sky signal reconstruction accuracy for types of instruments for which a fast sampling frequency is required both to remove atmospheric fluctuations and to perform full spectroscopic measurements on each sampled sky position. Methods. We first demonstrate the feasibility of this technique using simulations. Then, we apply such a scheme to on-sky calibration. Results. We show that the sky signal can be reconstructed to better than 0.5% for astrophysical sources, and to better than 2% for large background variations such as in "skydip", in an ideal noiseless scenario. The readout modulation method is validated by observations on-sky during the KISS commissioning campaign. Conclusions. We conclude that accurate photometry can be obtained for future KID-based MPI., 11 pages, 10 figures, accepted for publication in A&A

Jodrell Bank Observatory is responsible for the Front end modules (FEMs) for 30 GHz for LFI, with IAC being responsible for the hybrids and any phase switch. The University of Cantabria are responsible for the Back end modules (BEMs). Developments have been made to test prototypes both warm and cold for the FEMs. This is evolving towards flight hardware through an elegant breadboard phase EBB. Results of system performance show both white noise and 1/f characteristics.

"This paper is part of the Prelaunch status LFI papers published on JINST: http://www.iop.org/EJ/journal/-page=extra.proc5/jinst" This paper describes the Planck Low Frequency Instrument tuning activities performed through the ground test campaigns, from Unit to Satellite Levels. Tuning is key to achieve the best possible instrument performance and tuning parameters strongly depend on thermal and electrical conditions. For this reason tuning has been repeated several times during ground tests and it has been repeated in flight before starting nominal operations. The paper discusses the tuning philosophy, the activities and the obtained results, highlighting developments and changes occurred during test campaigns. The paper concludes with an overview of tuning performed during the satellite cryogenic test campaign (Summer 2008) and of the plans for the just started in-flight calibration., Comment: This is an author-created, un-copyedited version of an article accepted for publication in JINST. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher authenticated version is available online at http://dx.doi.org/10.1088/1748-0221/4/12/T12013]

21 páginas, 23 figuras, 13 tablas.-- et al., In this paper we present the Low Frequency Instrument (LFI), designed and developed as part of the Planck space mission, the ESA programme dedicated to precision imaging of the cosmic microwave background (CMB). Planck-LFI will observe the full sky in intensity and polarisation in three frequency bands centred at 30, 44 and 70 GHz, while higher frequencies (100–850 GHz) will be covered by the HFI instrument. The LFI is an array of microwave radiometers based on state-of-the-art indium phosphide cryogenic HEMT amplifiers implemented in a differential system using blackbody loads as reference signals. The front end is cooled to 20 K for optimal sensitivity and the reference loads are cooled to 4 K to minimise low-frequency noise. We provide an overview of the LFI, discuss the leading scientific requirements, and describe the design solutions adopted for the various hardware subsystems. The main drivers of the radiometric, optical, and thermal design are discussed, including the stringent requirements on sensitivity, stability, and rejection of systematic effects. Further details on the key instrument units and the results of ground calibration are provided in a set of companion papers., T.P.’s work was supported in part by the Academy of Finland grants 205800, 214598, 121703, and 121962. T.P. thanks the Waldemar von Frenckells Stiftelse, Magnus Ehrnrooth Foundation, and Väisälä Foundation for financial support. We acknowledge partial support from the NASA LTSA Grant NNG04CG90G.

This paper presents an overview of the Planck mission with specifics on the development, manufacturing and performance of the 70 GHz receivers of the low frequency instrument (LFI). Presently, development of the elegant breadboard model (EBB) has been completed and designing and manufacturing of the engineering model (EM) is ongoing. The EBB of LFI 70 GHz receivers has demonstrated state-of-the-art performance with a 30 K noise temperature, 16 GHz bandwidth, and a 1/f knee frequency of 30 mHz. Flight model manufacturing starts in Fall 2003.

A major problem in the transportation, transfer and storage of bulk chemicals is the problem of catastrophic instability under unforeseen situations. N

It is shown that the analog of Koopmans' theorem for the calculation of electron affinities yields poor results for conjugated hydrocarbons due mainly to neglect of atomic orbital deformation effects. Reminimization of the molecular ionic wave function yields a sizable increase of the electron affinity in several cases. It is further shown that the ground state MO's give a poor description of the charge distribution in the negative ion. In particular, reminimized MO's yield sites of positive charge in some negative ions.

Seven mathematical models for the treatment of monomer reactivity ratios in free-radical copolymerization are compared from the viewpoint of their relative simplicity, accuracy, and the number of parameters necessary for their use. It is concluded that the electronegativity and charge-transfer models proposed in previous papers represent the best compromise for routine usage if quantitative accuracy is the primary concern.

A model based on an electronegativity scheme is proposed for treatment of monomer reactivity ratios in free-radical bulk copolymerization. Values for each monomer are assigned to three parameters: a relative localization (or resonance stabilization) energy, a radical electronegativity, and a monomer electronegativity. Parameters for 17 monomers are given and calculated reactivity ratios are tabulated for a large number of copolymerizations. Agreement with experiment is usually obtained to within experimental error except for systems involving acrylonitrile. Computed parameters are rationalized on the basis of molecular orbital theory.

Quantum‐mechanical calculations within the Hartree–Fock framework and using two Gaussian basis sets are carried out on several conformations of the butane molecule. The smaller basis set predicts a transgauche barrier of 3.536 kcal/mole, an energy difference of 0.822 kcal/mole between the gauche and trans forms, and a barrier of 6.821 kcal/mole for interconversion of the two gauche conformations. The values of these quantities as given by the larger basis set are 3.619, 0.761, and 6.834 kcal/mole. Taking the angle of rotation about the central bond to be 0 for the trans conformation, the gauche form is predicted to occur at 110.9° for the smaller and at 111.3° for the larger basis set. The barrier to internal rotation of a methyl group is predicted to be 2.92 kcal/mole and 2.94 kcal/mole for the smaller and larger basis sets, respectively.

Two‐center wavefunctions are constructed for linear H3+ and H3 and for triangular (equilateral) H3+ using a basis set of generalized elliptical orbitals. The results are encouraging and possible future applications of the method are discussed.

Studies are carried out of truncated expansions of a hydrogen‐atom 1s orbital in spherical harmonics at another center, with Coulson—Barnett and with Slater‐orbital radial factors.

Quantum‐mechanical calculations are carried out on various conformations of the propane molecule using a Gaussian basis set and the Hartree–Fock–Roothaan formalism. These calculations indicate that internal rotation in propane can be adequately described by a simple equation of the form E(α1, α2) = 12V0 (2 − cos3α1 − cos3α2)−12V1[1 − cos3(α1 + α2)] where α1 and β2 are the two angles describing the rotation of the two methyl groups. The microwave spectrum of propane in the first excited torsional states reported by Hirota, Matsumura, and Morino was analyzed assuming this potential, leading to values for V0 and V1 of 3575 ± 100 cal/mole and 310 ± 40 cal/mole, respectively.

A variational procedure is proposed for the purely theoretical calculation of the diamagnetic susceptibility and nuclear magnetic shielding constants of a molecule, given a one‐center electronic wavefunction for it in the absence of a magnetic field. One performs a linear variational calculation, mixing in just those Slater determinants which the field causes to interact with the Slater determinants in the original wavefunction. A simple model is proposed, whereby one can simply estimate the magnetic properties from the original wavefunction. To illustrate the method, the susceptibility of the hydrogen molecule is computed from one simple and one more complex wavefunction expanded about the molecular center.The diamagnetic susceptibility and proton shielding constant for hydrogen then are calculated from a new single‐center wavefunction expanded about one of the protons. The detailed behavior of the computed paramagnetic contribution to the magnetic properties is discussed and the results indicate that th...

An unambiguous exact variational procedure is given for the calculation of certain weak interaction energies starting from any given approximate ground‐state wavefunction. The method is illustrated by numerous calculations on the hydrogen molecule using five different ground‐state wavefunctions.

The π‐electron ionization energies of conjugated hydrocarbons and charge distributions of the resulting positive ions are examined utilizing closed and open shell SCF theory with deformation of σ and π orbitals. Ionization energies: Koopmans' theorem is shown to be invalid for conjugated hydrocarbons to the extent of about 2–4 ev, the major breakdown occurring through the Σ and Π deformation effects and not through reminimization of the ionic configuration. It is shown that the sigma description is not the same for both the ground and ionized states. A first‐order correction to the Σ‐framework energy of the ion can be obtained by removing a π electron from a single carbon atom. Very good agreement is obtained between the calculated and observed onization potentials (average discrepancy 0.1–0.2 ev). Justification is given for the so‐called ``ω technique'' for the calculation of ionization energies by the Huckel procedure in that this method contains deformation corrections which approximate those derived in this work. Charge distributions: Both deformation effects and reminimization of the ionized state are important in consideration of the charge distribution in the ions. It is shown that certain sites of negative charge density are predicted in positive ions by the reminimization procedure, and that this is both a reasonable and necessary consequence due to the form of the ionic Hartree‐Fock Hamiltonian. The wave functions, and consequently the charge distribution, calculated by the ω technique, are shown to be poor approximations of the ionized state Hartree‐Fock eigenfunctions.

The CNDO/2 method is used to study the hydrogen bond strength in several representative systems. Enthalpies of hydrogen bond formation are generally predicted fairly well although some exceptions are noted. The proton-proton acceptor distances are predicted to be about 10 percent too small in all cases where comparison with experiment can be made.

Calculations within the LCAO SCF framework utilizing large basis sets of Slater orbitals centered at the heavy nucleus are carried out on HF and CH4 in order to assess the feasibility of computing near‐Hartree—Fock wavefunctions and energies for simple AHn‐type molecules. Considerable improvement is obtained over previous results found by the single‐center method, but it is concluded that it is not economically possible to extend the calculations to the accuracy given by poly‐centered methods.

Accurate two‐center calculations using a basis set of elliptical orbitals are made on the lowest‐lying singlet and triplet‐Π states of HeH+. The calculated dissociation energies of these states are 0.234 eV for the singlet and 0.147 eV for the triplet. Single‐center wavefunctions for these two states are also computed at the equilibrium internuclear separation predicted by the two‐center results (8.05 bohrs for the singlet and 7.67 bohrs for the triplet). The differences in the energies of the one‐ and two‐center calculations are 144 cal and 94 cal for the singlet and triplet, respectively. Expectation values of several operators are given along with calculated values of the spectroscopic constants.

A charge-transfer model is proposed for the treatment of monomer reactivity ratios in free-radical bulk polymerization. The procedure involves the assignment of three parameters to each monomer, which can be interpreted as being related to the energies of the highest occupied monomer orbital, the singly occupied radical orbital, and the lowest lying virtual orbital of the monomer. Parameters are found for 17 monomers and computed reactivity ratios for a large number of copolymer systems are tabulated and compared with experiment. Similarities of the present model and the electronegativity scheme are discussed.

Single‐center wavefunctions are constructed for the lowest‐lying singlet and triplet Πu(1sσ2pπ) and Πg(1sσ3dπ) excited states of the hydrogen molecule using a basis set of integral Slater‐type orbitals centered at the molecular midpoint. It is found that the convergence is more rapid than for a corresponding single‐center calculation on the ground state. The error in the binding energy is about 0.065 eV for the Πu states and 0.033 eV for the Πg states if a 19‐term configuration‐interaction wavefunction is used for the description of each.

Calculations are performed on the 2Σg+ and 2πu bound states of H2+ and the ground states of H2 and HeH+ using a basis set of nonintegral elliptical orbitals. The H2+ calculations are in the form of a single‐configuration wavefunction while both self‐consistent‐field and configuration‐interaction studies are carried out on H2 and HeH+.

The deficiencies of iterative extended Huckel theory as applied to conjugated molecules are discussed. An improved treatment is suggested which sacrifices complete rotational invariance but which is capable of a better representation of the πt-electron energy levels and molecular ionization potentials.

Many‐center wavefunctions for the hydrogen molecule and the hydrogen molecular ion are constructed using basis sets composed of either 1s orbitals or spherical Gaussians. Emphasis is placed on minimization of the total molecular energy with respect to all available nonlinear parameters. In the case of the s‐orbital basis, all the many‐center integrals are computed without resort to approximation techniques. It is concluded that the basis set of spherical Gaussians is superior to that of 1s orbitals and that further work with these functions may prove fruitful.

The bond‐orbital approach to calculations on saturated hydrocarbons given previously is improved by use of a more optimum basis set and through a more judicious choice of the bond orbitals. Calculations are carried out on methane, ethane, propane, and butane. Energy values, population analysis, and various computed properties are given and compared with the results of SCF calculations utilizing the same basis set.

Semiempirical calculations using the MINDO/2 procedure have been carried out on the potential surface for the reaction of a methyl radical with ethylene and trans-butadiene. The transition state is predicted to be reactant-like in character and no evidence of resonance stabilization of the activated complex is found for butadiene. It is conjectured that the experimentally observed lowering of the activation energy for butadiene relative to ethylene may be attributed to differential correlation effects.

Using one‐center single‐determinant approximations to the pertinent wave functions, the energies of CH3, CH3+, and CH5+ relative to CH4 have been calculated. If corrections for the different molecular geometries of the various species are made, reasonably good agreement with experiment for the carbon—hydrogen bond strength in methane, the ionization potential of CH3, and the appearance potential of CH3+ from CH4 is obtained. The modification of the calculation that gives the best agreement with experiment for these three known quantities leads to a value of 7.26 eV for the proton affinity of methane.

Using Roothaan's open‐shell procedure lowest triplet‐state excitation energies are computed for several polyacenes. The results indicate that single determinant wavefunctions constructed from ground‐state (closed‐shell) SCF orbitals give poor descriptions of the triplet states, leading to errors of up to ½ eV in the energy. The triplet‐state orbitals are given. Comparison of these calculations with Pariser's CI computations suggests that significant correlation has been introduced into the CI excited state description, but not into the ground state.

The basic principles and methods of quantum mechanics have gradually become familiar to an increasingly large number of scientists working in many diverse areas of research. At the present time, application of quantum mechanical methods to such problems as protein structure, drug design, hydrogen bonding, and many other phenomena important in biological studies is becoming common. Nearly all such applications to phenomena of biological interest are made by means of some type of semiempirical formulation. Therefore it seems of interest to review these semiempirical methods and to discuss in detail their advantages and shortcomings. This chapter is an attempt at such a review and will be restricted to a discussion of empirical and semiempirical molecular orbital (MO) approaches. Emphasis will be placed on recent all-valence electron approaches and no discussion of the older methods will be given since these latter formulations have already been exhaus- tively reviewed elsewhere.

Ab initio calculations of barriers to internal rotation in propane are carried out by a bond orbital approach. The results are in fair agreement with experiment and indicate that the rotation of the two methyl groups is not independent.

The Planck Low Frequency Instrument (LFI) radiometers have been tested extensively during several dedicated campaigns. The present paper reports the principal noise properties of the LFI radiometers., Comment: this paper is part of the Prelaunch status LFI papers published on JINST: http://www.iop.org/EJ/journal/-page=extra.proc5/jinst

In this paper we present the test results of the qualification model (QM) of the LFI instrument, which is being developed as part of the ESA Planck satellite. In particular we discuss the calibration plan which has defined the main requirements of the radiometric tests and of the experimental setups. Then we describe how these requirements have been implemented in the custom-developed cryo-facilities and present the main results. We conclude with a discussion of the lessons learned for the testing of the LFI Flight Model (FM).