Instrument Functions Research Articles

Deconvolution of Instrumental Broadening in Dispersive Raman Spectroscopy

The resolution enhancement of instrumentally broadened Raman spectra using neon emission lines as instrument functions is considered in this paper. When the signal-to-noise ratio is sufficiently high, Fourier deconvolution is effective in reducing the instrumental broadening to the optical limit, provided that the instrument function is narrower than the individual widths of the overlapping bands. If this is not the case, a nonlinear iterative technique is required. As an example, the v1, band of CCl4 has been measured at various slit widths and deconvolved with the appropriate neon lines; for comparison, the computations have also been performed with Gaussian approximations to the true instrument functions.

Semi-empirical and phenomenological instrument functions for the scanning tunneling microscope

Recent progress in the development of a convenient algorithm for the determination of a quantitative local density of states (LDOS) of the sample, from data measured in the STM, is reviewd. It is argued that the sample LDOS strikes a good balance between the information content of a surface characteristic and effort required to obtain it experimentally. Hence, procedures to determine the sample LDOS as directly and as tip-model independently as possible are emphasized. The solution of the STM's "inverse" problem in terms of novel versions of the instrument (or Green) function technique is considered in preference to the well known, more direct solutions. Two types of instrument functions are considered: Approximations of the basic tip-instrument function obtained from the transfer Hamiltonian theory of the STM-STS. And, phenomenological instrument functions devised as a systematic scheme for semi-empirical first order corrections of "ideal" models. The instrument function, in this case, describes the corrections as the response of an independent component of the measuring apparatus inserted between the "ideal" instrument and the measured data. This linear response theory of measurement is reviewed and applied. A procedure for the estimation of the consistency of the model and the systematic errors due to the use of an approximate instrument function is presented. The independence of the instrument function techniques from explicit microscopic models of the tip is noted. The need for semi-empirical, as opposed to strictly empirical or analytical determination of the instrument function is discussed. The extension of the theory to the scanning tunneling spectrometer is noted, as well as its use in a theory of resolution.

Ocean Telemetry Workshop

An informal workshop on ocean telemetry and platform location was held on January 15, 1986, during the AGU Ocean Sciences Meeting in New Orleans, La. Plans for the workshop grew from the realization that present methods of data transmission and platform location may be inadequate for projected needs. The objectives of the workshop were to identify present and promising methods of ocean telemetry and platform location, estimate needs for these capabilities during the next decade, and identify a few promising methods for focused development. As a starting point, it was recognized that large ocean experiments with decadal time scales and global space scales have much to gain from telemetry. The principal scientific advantages are quasi‐real‐time data recovery, insurance against premature failures, adaptive control of instrument functions, expendability of instruments, and the potential for rapid data assimilation by models and distribution of data to users. Only in limited cases have these advantages been exploited even partially.

Modification of a packed column gas chromatograph/mass spectrometer

A packed-column gas-chromatograph/mass-spectrometer (GC/MS), Hewlett-Packard 5982, was modified to accommodate fused silica capillary columns. The original GC/MS interface and chemical-ionization sample-line in the ion-source were changed to allow the end of a fused silica capillary column to enter the ion-chamber directly. For chemical-ionization operation, the reagent gas was brought into the MS through the direct-insertion probe port. The calibration compound was introduced through the electron-impact sample-inlet, which simplified the operation. The modified system yields higher sensitivity and more efficient separation, as well as simpler operation, without sacrificing any original instrument functions.

Correct method for calculating energy resolution and instrument functions of scintillation spectrometers

The expressions for calculating the instrument functions of singleand multi-crystal scintillation spectrometers with several PMs are presented, and are valid for primary particles of any type and any energies. The authors also calculate the amplitude spectra of scintillation spectrometers in the range of low and medium gamma-radiation energies.

Physical line widths of atoms and ions in an inductively coupled argon plasma and hollow cathode lamps as measured by an echelle mono-chromator with wavelength modulation

The spectral line profiles for emission lines of atoms and ions which were produced and excited in an inductively coupled argon plasma at atmospheric pressure have been measured by using an echelle monochromator. The emission line profiles of hollow cathode lamps were also measured to evaluate the resolving power of the monochromator and to deduce the instrument functions at various wavelengths. The line profiles were observed by a wavelength modulation technique; a quartz plate set just behind the entrance slit was modulated at 125 Hz and the photomultiplier output was acquired at 50 points with 2500 times integration for 20 s. The observed line profiles were simulated by the curve-fitting algorithm for the Voigt function, and a-parameters were deduced, after the instrument functions were corrected from the data obtained with the hollow cathode lamp measurements. The physical line widths, a-parameters, and Doppler temperatures obtained are in good agreement with those reported previously.

Analytical Description of Tunable Diode Laser Derivative Spectrometry

The instrument functions are investigated, and a quantitative description is given of how a second-derivative spectrometer employing a tunable diode laser attains the power to suppress spectral noise. As a result, it is found that the power can be improved by modifying the source-frequency modulation profile. The essence of this approach is to make the profile at its extreme as sharp as possible, and a hyperbolic sine profile with suitable parameters is proposed as the optimal profile that can be attained in practice.

Computer control of the nicolet 1170 signal averager

An interface has been constructed for the Nicolet 1170 signal averager to allow computer control of most of the instrument's functions, because the standard computer interface available from the manufacturer does not permit control over a number of front panel switches necessary for automatic data transfer. Computer control can be obtained with the addition of one printed circuit card, containing 3 integrated circuits, that plugs into an empty motherboard socket in the Nicolet mainframe, and a few simple backplane wiring changes. The digital I/O interface supplied by the manufacturer is still required, but this interface does not allow easy access to the desired signals on the control connector. Therefore, construction of a new interface in a separate enclosure is more desirable. The computer requires two digital I/O ports for data transfer and control. A number of Pascal routines have been written for computer control of the Nicolet.

CCD Camera Systems and Support Electronics for a White Light Coronagraph and X-Ray XUV Solar Telescope

Two instruments, a White Light Coronagraph and an X-ray XUV telescope built into the same housing, share several electronic functions. Each instrument uses a CCD as an imaging detector, but due to different spectral requirements, each uses a different type. Hardware reduction, required by the stringent weight and volume allocations of the interplanetary mission, is made possible by the use of a microprocessor. Most instrument functions are software controlled with the end use circuits treated as peripherals to the microprocessor. The instruments are being developed for the International Solar Polar Mission.

On Aperture Correction in Scanning Interferometry

The instrument functions of scanning Michelson and Fabry-Perot interferometers in the limiting case of coherence are investigated and characteristics such as the scanning aperture correction and resolving power are analysed. It is shown that there are no essential practical differences in these characteristics from those in the incoherent case.

A Pupil-scan Aberration Analyser

The principles of operation of an instrument which can measure the wavefront aberrations, transverse-ray aberrations, and spot diagrams of an optical system are described. The instrument functions by scanning the pupil of the optical system with a ‘ray’ of light and measuring the coordinates of the point of intersection of the ray, with the image plane, using a position-sensitive detector. An image-dissector tube is used as the position-sensitive detector. The instrument also has a facility for generating a polynomial function which can be matched to the measured aberration curves in order to determine directly the aberration coefficients.

Unification of rotary motion feedthroughs for ultrahigh vacuum evaporation systems: G A Shaumyan et al, Elektron Tekh Tekhnol Organiz Proizv, 5, 1970, 70–74 ( in Russian)

A packed-column gas-chromatograph/mass-spectrometer (GC/MS), Hewlett-Packard 5982, was modified to accommodate fused silica capillary columns. The original GC/MS interface and chemical-ionization sample-line in the ion-source were changed to allow the end of a fused silica capillary column to enter the ion-chamber directly. For chemical-ionization operation, the reagent gas was brought into the MS through the direct-insertion probe port. The calibration compound was introduced through the electron-impact sample-inlet, which simplified the operation. The modified system yields higher sensitivity and more efficient separation, as well as simpler operation, without sacrificing any original instrument functions.

Micro X-ray spectral investigation of Ti- and Ti-Ag to A-995 ceramic seals: E S Zhmud et al, Elektron Tekh Elektron SVCh, 11, 1970, 117–123 ( in Russian)

A packed-column gas-chromatograph/mass-spectrometer (GC/MS), Hewlett-Packard 5982, was modified to accommodate fused silica capillary columns. The original GC/MS interface and chemical-ionization sample-line in the ion-source were changed to allow the end of a fused silica capillary column to enter the ion-chamber directly. For chemical-ionization operation, the reagent gas was brought into the MS through the direct-insertion probe port. The calibration compound was introduced through the electron-impact sample-inlet, which simplified the operation. The modified system yields higher sensitivity and more efficient separation, as well as simpler operation, without sacrificing any original instrument functions.

The Instrument Function of a Wide Angle Michelson Interferometer Spectrometer

The instrument function of a wide angle Michelson interferometer spectrometer is derived in terms of known or easily measured functions using a novel method of computing the phase difference between the two beams. The interferometer essentially achieves immersion with solid materials and has the advantages of a larger field of view and fewer reflecting interfaces. A set of instrument functions is plotted in which either the field of view or the wavelength, with the other held fixed, may be interpreted as the parameter. The allowable field of view is found to increase linearly with the index of refraction of the cube material. A simple working model yielded both white light and mercury green light fringes.

A posteriori image-correcting “deconvolution” by holographic fourier-transform division

Division of spatial field distributions in the Fourier-transform domain for “resolution-retrieving”, “corrective” image deconvolution of the “smearing” resulting from extended “instrument functions” in optical imaging, spectroscopy and radio-astronomy may be accomplished by a “two-filter” holographic scheme.

Measurements of the instrument function and of the spectral slit width of a prism spectrophotometer

In the present work we shall report on measurements of the instrument function on a monochromator according to the method of “bundle limitation”. From the half-intensity widths of these instrument functions the function of weight F(ω) will be ascertained, which describes the influence of the diffraction on the half-intensity width. Further the measurement of F(ω) with the aid of an interferometric technique in the infrared spectral region will be described. The results will be compared with the values which are to be theoretically expected. The behavior of the calculated instrument functions will be reported, and the energetic relations of a prism monochromator, as varied by diffraction, will be studied.