Quartz Spectrograph Research Articles

π* ← π systems in the electronic absorption spectra of some trisubstituted benzenes

Abstract The electronic absorption spectra of 2,3-, 2,4-, 2,5- and 3,4-difluorobenzaldehyde in the UV region in vapour have been recorded on medium quartz and Hilger Large Quartz Spectrographs, and on a Hitachi U-3200 UV—vis spectrophotometer and analyzed. All the molecules investigated have exhibited two π* ← π band systems corresponding to 1B2u ← 1A1g (λ 2600 A) and 1B1u ← 1A1g (λ 2100 A) systems of benzene.

Application of a photodiode array detector to an arc spectrograph

A multiple array photodiode detector was interfaced to a medium quartz spectrograph with a d.c. arc source. The detector replacing the photographic plate consists of nine photodiode arrays, giving a total of 9216 diodes for the set. Full spectral coverage from 2000 to 10 000 Å is achieved by staggering the arrays so that approximately 40 diodes of one array overlap with the next array. The calibration and sensitivity of this system are discussed.

Infrared and electronic absorption spectra of some trisubstituted benzenes

Abstract The electronic absorption spectra of 2,3-, 2,4-, 2,5-, 2,6- and 3,4-difluorobenzonitriles, 3,4-difluoroaniline and 3,4-difluoroanisole in the ultraviolet region in vapour phase have been recorded on medium quartz and Hilger large quartz spectrographs and on a Hitachi model 150-20 UV-VIS ratio recording spectrophotometer. All the molecules investigated have exhibited two π* ← π band systems corresponding to 1 B 2 u ← 1 A 1 g (λ2600 A) and 1 B 1 u ← 1 A 1 g (λ2100 A) systems of benzene. The infrared absorption spectra of all the molecules studied have also been recorded and analysed. These infrared data have been taken to help analyse the u.v. spectra of the molecules studied.

Absorption bands of O2 and OH in a new ultraviolet continuum and in the XeCl laser spectrum

Two excimer lasers of the automatic pre-ionization type have been constructed. To avoid impurities, the two series of condensers were placed outside the discharge chamber. Using one of these devices we have observed a new ultraviolet (UV) continuum from a discharge through a He–O2 mixture at 900 Torr. The continuous nature of this emission was assured by the observation of almost 80 absorption bands of the O2 Schumann-Runge system arising from highly excited vibrational levels and of some OH bands in the A–X system. The same type of discharge through pure He emits no continuum but some OH bands. The time dependence of the light pulses was studied to infer the origin of the continuum. Based on these observations, we show that the strong absorption in the B–X, 0–2 band of the XeCl laser is due to the P11, Q13, and Q13′ lines in the 0–0 band of the OH A–X system; the estimated intensity of this absorption amounting to 5–7% of the total intensity of the XeCl laser. The XeCl spectra were photographed on an E1 quartz spectrograph and in the third order of a 6.65 m grating.

Spectrographic analysis of refractory magnesium oxide: A buffer approach

A method has been described for the determination of eighteen trace elements in refractory magnesium oxide by optical emission spectroscopy. The main feature of the method is the use of a spectroscopic buffer instead of a carrier. When conducting graphite powder has been added as a buffer to the MgO sample prior to its excitation in a d.c. arc, there has been a smooth distillation of the matrix magnesium as well as the trace elements into the arc column. Addition of a carrier, however, does not either completely prevent the emission of Mg spectrum or result in smooth distillation. A Hilger large quartz spectrograph has been employed to record the spectra excited at 10 amp d.c. The Ga line at 265.99 nm has been used as an internal standard for the more volatile trace elements and the Mg line at 280.98 nm has been employed as an internal standard for the less volatile trace elements. The detection limits obtained range from 0.5–5 ppm for the various elements. The mean relative standard deviation (RSD) of the method is ± 14%.

Electronic and vibrational spectra of 6-amino-2-methylpyridine

The near ultraviolet absorption spectra of 6-amino-2-methylpyridine has been recorded on Hilger medium quartz spectrograph in vapour phase. The very strong band at 34 133 cm —1 has been assigned as 0,0 band and the spectra have been analysed in terms of combinations and overtones of ground and excited state fundamentals. The laser Raman spectrum of the molecule has been recorded on CODERG Raman spectrometer T 800 triple monochromator. The analysis of the spectrum and assignment to various fundamental modes has been made. The vibrational fundamentals have also been used for computing thermodynamic properties assuming hindered internal rotation of NH 2 group about z-axis and using VAX-11/780 computer and their trend discussed.

Optical spectrum of a closed cycle MHD generator plasma

The spectra of argon-cesium plasmas, used as working fluids of closed-cycle MHD generators, were investigated in the visible and near-i.r. regions by using a Hilger-Watts medium quartz spectrograph. A number of argon and cesium lines was observed, as well as some lines originating from the impurities present in the cesium capsule. The molecular bands of aluminum monoxide have also been detected. The population temperatures estimated from relative intensities of cesium lines lie below those obtained by using either the line-reversal method or recombination-radiation measurements. The intensities of some neutral cesium lines follow the Boltzmann population relation at the population temperature. The Zeeman effect and reversed profiles of cesium resonance lines were not observed because of low resolution of the spectrograph used and because of light scattering on the film.

Direct determination of traces of heavy metals in canned vegetables by arc spectrography

A new, simple, and rapid method for the direct and simultaneous determination of traces of iron, copper, lead, tin, silver, and manganese in brined canned vegetables is described. Pure graphite powder is used as spectroscopic buffer and for the preparation of standard powders. Pure sulfur is added to the sample before calcination to bind trace metals as sulfides and prevent volatilization. A quartz spectrograph of high resolving power is used for this determination.

Determination of traces of heavy metals in oils and fats by arc spectrography.

AbstractA new and simple method is described for direct and simultaneous determination of traces in fats and oils of iron, copper, nickel, lead, silver, aluminum, magnesium, calcium and manganese. Graphite powder is used as spectroscopic buffer and for preparation of standard powders. Using necked cupped carbon electrode and cone shaped counter electrode, a steady DC arc discharge is obtained with graphite matrix. A quartz spectrograph of high resolving power is used for this determination.

Electronic absorption spectrum of copper formate tetrahydrate

Single crystals of copper formate tetrahydrate were grown at room temperature. Spectra in the near infrared at room temperature and in the visible at room and liquid air temperatures were recorded on a Unicam SP-700 spectrophotometer and Hilger medium quartz spectrograph respectively. The observed absorption bands have been attributed to an ion of Cu 2+ in tetragonal symmetry with 2B 1g as the ground state. Taking into consideration the spin—orbit coupling associated with the tetragonal field, a successful interpretation of all the observed bands has been made. The band observed in the near infrared at 11000 cm −1 has been indentified with a vibrational overtone mode of CO 2. The crystal parameters derived are Dq = −1380 cm −1, Ds = −1950 cm −1, Dt = −205 cm −1 and λ = −830 cm −1.

A rotating briquetted-disk method for the determination of boron and other elements in plant material by emission spectroscopy

Graphite-based disks containing 5% plant ash are analyzed by using a triggered condensed a.c. discharge to excite spectral lines whose intensities are measured by means of an 11 channel E750 Direct Reading Attachment to a Hilger-Watts E498 Medium Quartz Spectrograph. Matrix effects caused by variation of plant composition are suppressed by buffering with potassium sulphate and calcium carbonate. Lithium and chromium are used as reference elements and the following ranges of plant ash content can be covered in a single exposure: boron 25–350 ppm, aluminium 200–5000 ppm, copper 10–200 ppm, iron 250–10,000 ppm, magnesium 0.25–5%, manganese 100–4000 ppm, phosphorus 0.5–15%, silicon 0.25–15% and zinc 50–1200 ppm. The relative standard deviation for boron was 5% when calculated from 40 sets of secondary-standard plant samples analyzed over a 4 yr period.

A Carrier Distillation Method for Estimation of Boron in CaF2

Abstract A carrier distillation method is described for determination of boron in calcium fluoride. The sample is mixed with 5 % copperoxyfluoride containing 200 ppm of gallium. 50 mg of this mixture is loaded in pre-arced U. C. C. 1990 electrode and excited using 15 amp. d. c. arc. The resulting spectra are recorded in the region 2200 to 2850 A employing Hilger large quartz spectrograph. The detection limit for boron is 0.1 ppm and the precision of the method is ± 12%.

Spectrographic a.c. spark method for the estimation of yttrium in rare earth mixtures

The spectrographic estimation of yttrium in rare earth mixtures was achieved within a concentration range of 1–90% by means of the a.c. spark method using a large quartz spectrograph. The sample was mixed with ceria and zinc oxide in the ratio 2∶1∶2. The Y lines 2414.68 A and 2856.36 A were used as analytical lines for the ranges of 1–15% and 10–90%, respectively. The Ce line at 2603.65 A served as internal standard line. The standard deviation was 2–5%.

Optical absorption spectrum of Cu 2+ doped in NH 4Cl single crystal

Single crystals of copper-doped ammonium chloride were grown at room temperature. Spectra in the near infrared at room temperature and in the visible at room and liquid-air temperatures were recorded on a Unicam SP-700 spectrophotometer and Hilger medium quartz spectrograph, respectively. The observed absorption bands have been attributed to an ion of Cu 2+ in tetragonal symmetry with 2B 1 as the ground state. Taking into consideration spin-orbit coupling associated with a tetragonal field, a successful interpretation of all the observed bands has been made. The crystal parameters derived are Dq = −1360 cm −1; Ds = −2000 cm −1; Dt = −140 cm −1 and λ = −830 cm −1.

Quartz spectograph with oscillating plateholder for stellar spectrophotometry. Review of some applications

Description of a small quartz spectrograph for stellar spectrophotometry. It is built to be used at the Cassegrain focus of a reflector. The spectrum broadening is accomplished by small oscillations of the platheholder in its plane: this method allows to obtain spectra narrower in the ultraviolet than in the red, hence to reinforce the short wave-lengths. Behind the slit, an adjustable rotating sector permits to reduce in a know proportion the light entering the slit and to make easier the comparison between the spectra of stars with different magnitudes. The spectrograph can be rotated around the collimator axis so that the plane determined by this axis and the slit remains always vertical: thus are avoided the disturbing effects of the amospheric refraction are briefly described by D. Chalonge and L. Divan.

Electronic Absorption Spectrum of Mesitylene Vapour

Abstract The electronic absorption spectrum of mesitylene vapour has been photographed on a Q-24 Medium Quartz Spectrograph. The molecule belongs to D3h symmetry and the transition is A→1A2 which is forbidden and due to that the (0,0) band does not appear in the spectrum. The position of (0,0) band in this case has been fixed at 36562 cm−1 with the help of 0→1 and 1→0 transitions. There are 66 bands and most of them are assigned in terms of two ground state frequencies of magnitudes 278 and 519 cm−1 and 7 excited state frequencies of magnitudes 267, 436, 554, 968, 1268, 1386 and 1575 cm−1

A technique for the qualitative spectrographic analysis of very small samples

The sample and a small yarn of carbon fibers are stuck on to a pointed graphite electrode; the gap between this and the upper electrode is bridged by the carbon fibers which strike the arc when the dc source is switched on. Background emission is greatly reduced by enclosing the arc in an argon atmosphere. Simple condensing optics are employed with a Hilger medium quartz spectrograph. Many elements can be detected with ease in 1 μg amounts and five elements were detected in 1 μg samples of RU powder.

π-π* Absorption Spectrum of Pyridine-D5

The absorption spectrum of π–π* system of pyridine-D5 molecule has been measured in the range 33790–36990 cm−1, on the Hilger large quartz spectrograph. A large number of sharp bands have been measured and analyzed in terms of ground and excited state frequencies which have been compared with the corresponding frequencies of pyridine-H5 molecule.

Electronic Absorption Spectrum of 2,4-Dibromoaniline in Vapor

The near ultraviolet absorption spectrum of 2,4-dibromoaniline in vapor phase has been photographed for the first time on a Q-24 Zeiss Medium Quartz Spectrograph. The quartz to Pyrex graded seal cells were used. The conventional hydrogen lamp was the source of continuous radiation. The tube lengths were varied from 50 to 125 cm and the temperatures from 30° to 80°C. The sharp bands appear with a cell of length 100 cm at the temperature 43°C. The spectra were photographed on Kodak B10 plates.

Characteristics of diffuse electrical discharges stabilized in flowing air, argon and nitrogen

In studying electrically augmented flames it has been found that the fuel flow to a burner can be reduced to zero, leaving an electrical discharge stabilized in axially flowing air at atmospheric pressure. An electrode configuration of axial anode and cylindrical cathode stabilized the discharge under conditions where it would be unstable in quiescent air. No ionizable seed material was necessary in the air to maintain the discharge once initiated. In addition to stabilization in air, similar discharges have been maintained in nitrogen and argon. Voltages of between 40 and 400 V and currents from 2 to 10 A sustained discharges across electrode gaps of 3 to 15 cm with gas flowrates varying between 10 and 2500 cm3 s−1. The variation of the discharge voltage with these parameters has been correlated with a modified Grotrian expression for long arcs in air. The spectral lines of both copper and carbon (depending upon the electrode material used) were identified using a medium quartz spectrograph, and temperature estimations of 5400 K in the discharge were made by comparing spectral line intensities. High-speed photography has also revealed interesting features of the system.