The induced infrared fundamental band of hydrogen dissolved in solid argon

1968 ◽  
Vol 46 (10) ◽  
pp. 1181-1189 ◽  
Author(s):  
R. J. Kriegler ◽  
H. L. Welsh
Keyword(s):  
Path Length ◽  
Lattice Site ◽  
Lattice Vibration ◽  
Liquid Solution ◽  
Absorption Path Length ◽  
Slow Cooling ◽  
Zero Phonon Line ◽  
Fundamental Band ◽  
Difference Tones ◽  
Solid Argon

The induced infrared fundamental band of hydrogen dissolved (~1:100) in solid argon was studied with a 20-cm absorption path length at −191 °C. Transparent crystals were prepared by slow cooling of the liquid solution saturated with hydrogen at ~25 atm pressure. The H2 transitions, Q, S(0), and S(1), show similar patterns of five maxima, each of which can be analyzed as a zero-phonon line at the H2 frequency and summation and difference tones with lattice transition frequencies, 112 and 22 cm−1. The 112-cm−1 frequency is interpreted as arising from a localized lattice vibration involving an H2 molecule on a substitutional lattice site. Calculation from a model of an H2 molecule moving in the field of its argon neighbors, considered stationary, gave 109 cm−1 for this frequency. The origins of the zero-phonon lines and the 22-cm−1 lattice transition frequency are not so clear, and several possibilities are discussed. The H2 frequencies are shifted from their free-molecule values by the sum of a vibrational shift, Δνvlb = −17 cm−1, and rotational shifts corresponding to ΔB = −0.52 cm−1.

On-chip cavity-enhanced absorption spectroscopy using a white light-emitting diode and polymer mirrors

Lab on a Chip ◽  
2015 ◽  
Vol 15 (3) ◽  
pp. 711-717 ◽  
Author(s):  
Cathy M. Rushworth ◽  
Gareth Jones ◽  
Martin Fischlechner ◽  
Emma Walton ◽  
Hywel Morgan
Keyword(s):  
Absorption Spectroscopy ◽  
White Light ◽  
Microfluidic Chip ◽  
Path Length ◽  
Light Emitting Diode ◽  
Absorption Path Length ◽  
Light Emitting ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
On Chip

We have integrated disposable polymer mirrors within a microfluidic chip to form a multi-pass cell, which increases the absorption path length by a maximum of 28 times, providing micromolar detection limits in a probed volume of 10 nL.

Interference effects in the spectrum of HD: IV: the pure rotational band at room temperature

1986 ◽  
Vol 64 (3) ◽  
pp. 227-231 ◽  
Author(s):  
A. R. W. McKellar
Keyword(s):  
Spectral Resolution ◽  
Rotational Band ◽  
Path Length ◽  
Room Temperature ◽  
Dipole Transition ◽  
Rotational Spectrum ◽  
Density Range ◽  
Interference Effects ◽  
Fundamental Band ◽  
Line Strengths

The rotational spectrum of HD has been studied in absorption at room temperature for a density range of 6–57 amagat. Spectra were obtained in the 170- to 360-cm−1 region, including the R0(1), R0(2), and R0(3) transitions, with a 1-m path length and a spectral resolution varying from 0.05 to 0.20 cm−1. The observed line strengths were used to determine values for the dipole transition moments of HD in the range of 7.4 to 7.8 × 10−4 D, which is somewhat lower than currently accepted theoretical values of about 8.3–8.4 × 10−4 D. Only very small effects (≈0.2% per amagat) were found due to collisional interference on the line strengths; this result contrasts with much larger interference effects observed in the fundamental band, and it also casts some doubt on other recent studies of the rotational spectrum where larger interference effects were reported.

scholarly journals FLASH early science – discovery of an intervening H i 21-cm absorber from an ASKAP survey of the GAMA 23 field

2020 ◽  
Vol 494 (3) ◽  
pp. 3627-3641 ◽  
Author(s):  
J R Allison ◽  
E M Sadler ◽  
S Bellstedt ◽  
L J M Davies ◽  
S P Driver ◽  
...  
Keyword(s):  
Path Length ◽  
Column Density ◽  
Radio Sources ◽  
Early Type ◽  
Absorption Path Length ◽  
Spin Temperature ◽  
Upper Limits ◽  
Blind Search ◽  
Cross Matching ◽  
Early Type Galaxy

ABSTRACT We present early science results from the First Large Absorption Survey in H i (FLASH), a spectroscopically blind survey for 21-cm absorption lines in cold hydrogen (H i) gas at cosmological distances using the Australian Square Kilometre Array Pathfinder (ASKAP). We have searched for H i absorption towards 1253 radio sources in the GAMA 23 field, covering redshifts between z = 0.34 and 0.79 over a sky area of approximately 50 deg2. In a purely blind search, we did not obtain any detections of 21-cm absorbers above our reliability threshold. Assuming a fiducial value for the H i spin temperature of Tspin = 100 K and source covering fraction cf = 1, the total comoving absorption path-length sensitive to all Damped Lyman α Absorbers (DLAs; NH i ≥ 2 × 1020 cm−2) is ΔX = 6.6 ± 0.3 (Δz = 3.7 ± 0.2) and super-DLAs (NH i ≥ 2 × 1021 cm−2) is ΔX = 111 ± 6 (Δz= 63 ± 3). We estimate upper limits on the H i column density frequency distribution function that are consistent with measurements from prior surveys for redshifted optical DLAs, and nearby 21-cm emission and absorption. By cross-matching our sample of radio sources with optical spectroscopic identifications of galaxies in the GAMA 23 field, we were able to detect 21-cm absorption at z = 0.3562 towards NVSS J224500−343030, with a column density of $N_{\rm H\,\small{I}} = (1.2 \pm 0.1) \times 10^{20}\, (T_{\rm spin}/100\, \mathrm{K})$ cm−2. The absorber is associated with GAMA J22450.05−343031.7, a massive early-type galaxy at an impact parameter of 17 kpc with respect to the radio source and which may contain a massive (MH i ≳ 3 × 109 M⊙) gas disc. Such gas-rich early types are rare, but have been detected in the nearby Universe.

Further studies on the collision-induced absorption of the fundamental band of hydrogen at room temperature

1969 ◽  
Vol 47 (24) ◽  
pp. 2745-2751 ◽  
Author(s):  
G. Varghese ◽  
S. Paddi Reddy
Keyword(s):  
Binary Mixture ◽  
Infrared Absorption ◽  
Path Length ◽  
Room Temperature ◽  
Absorption Coefficients ◽  
Fundamental Band ◽  
Induced Absorption ◽  
Two Peaks

The collision-induced infrared absorption of the fundamental band of hydrogen in H2–O2 and H2–Xe mixtures was studied at room temperature at a path length of 105.2 cm at pressures up to 250 atm for different base pressures of hydrogen. The enhancement absorption profiles of the band in H2–O2 mixtures show the usual features of collision-induced absorption. However, the enhancement profiles in H2–Xe mixtures show some interesting new features. These are: the separation between the peaks of the two components of the Q branch remains almost constant with increasing density of the mixture; at all densities, the intensities of these two peaks are almost equal; and the lines of the quadrupolar branches O and S are more pronounced than those in any other binary mixture of hydrogen studied previously. Integrated absorption coefficients were measured for each of the mixtures and the binary and ternary absorption coefficients were derived. The values of the binary coefficients are 6.12 × 10−35 cm6 s−1 for H2–O2, and 11.34 × 10−35 cm6 s−1 for H2–Xe. The ternary coefficient is zero for H2–O2, whereas it has a large negative value for H2–Xe.

scholarly journals Pressure-induced infrared absorption of the fundamental band of hydrogen in H2–Ne and H2–Kr mixtures at room temperature

1968 ◽  
Vol 46 (12) ◽  
pp. 1373-1379 ◽  
Author(s):  
S. Paddi Reddy ◽  
W. F. Lee
Keyword(s):  
Infrared Absorption ◽  
Path Length ◽  
Room Temperature ◽  
Absorption Coefficients ◽  
Fundamental Band ◽  
Low Pressures

The pressure-induced infrared absorption of the fundamental band of hydrogen in H2–Ne and H2–Kr mixtures was studied at room temperature at a path length of 25.8 cm at pressures up to 400 atmospheres for different base pressures of hydrogen. In the enhancement absorption profiles of the band in H2–Ne mixtures, the S(1) line at all pressures and the QP component at low pressures show doublet structures. In the enhancement contours in H2–Kr mixtures, there is an indication of the QQ component between the QP and QR maxima at higher pressures, and the O and S lines are much stronger than the corresponding lines in H2–Ne mixtures. Integrated absorption coefficients were measured for each of the mixtures studied, and the binary and ternary absorption coefficients were derived. The values of the binary coefficients are 2.37 × 10−35 cm6 s−1 for H2–Ne and 7.56 × 10−35 cm6 s−1 for H2–Kr.

Induced Fundamental Infrared Band of Nitrogen Dissolved in Solid Argon

1971 ◽  
Vol 49 (24) ◽  
pp. 3201-3207 ◽  
Author(s):  
J. De Remigis ◽  
H. L. Welsh ◽  
R. Bruno ◽  
D. W. Taylor
Keyword(s):  
Path Length ◽  
Harmonic Approximation ◽  
Host Lattice ◽  
Mode Frequency ◽  
Local Mode ◽  
Infrared Band ◽  
Temperature Range ◽  
Solid Argon ◽  
Experimental Temperature Range ◽  
Good Agreement

The induced fundamental infrared band of nitrogen dissolved in solid argon was studied over the temperature range 55–81 K with a path length of 40 cm and molar N2 concentrations of 1−2%. The spectrum consists of combination tones of lattice transitions with the N2 1 ← 0 vibrational transition. Lattice transition frequencies of 70 and 39 cm−1 at 55 K are identified with a local mode and vibrations of the host-lattice atoms respectively. We have computed the local-mode frequency over the experimental temperature range using one-defect theory in a harmonic approximation employing temperature-corrected experimental phonon frequencies and obtain good agreement with the observed values. The 39 cm−1 peak can be identified with features of the transverse region of the Ar phonon density of states.

Slow Crystallization of Al-Sc Alloys: Growth of Spherical Intermetallic Particles

2012 ◽  
Vol 326-328 ◽  
pp. 75-80 ◽  
Author(s):  
A.B. Shubin ◽  
E. A. Popova ◽  
K. Y. Shunyaev ◽  
E.A. Pastukhov
Keyword(s):  
Transition Metals ◽  
Solid Solutions ◽  
Liquid Solution ◽  
Spherical Particles ◽  
Liquid Alloys ◽  
Concentration Profiles ◽  
Slow Cooling ◽  
Minor Addition ◽  
Intermetallic Particles

The solidification of binary Al-Sc melts containing small amounts of scandium (< 2 wt.%) have been investigated. We studied concentration profiles in long Al-Sc as cast ingots formed by slow cooling of the liquid alloys. It was found that minor addition of transition metals like Ti can lead to the formation of large (about 10-20 μm) spherical intermetallic particles (Al3Sc containing some amount of isomorphic Ti). These sphere-like particles are forming during the crystallization of liquid solution of Sc in Al (before the precipitation on nanosize spherical particles from the solid solutions). The results of SEM and EDX investigations of these alloys are also presented in this paper.

Fundamental infrared absorption of H2 in solid Kr and of D2 in solid argon

1970 ◽  
Vol 48 (13) ◽  
pp. 1622-1627 ◽  
Author(s):  
J. De Remigis ◽  
H. L. Welsh
Keyword(s):  
Absorption Band ◽  
Solid Solutions ◽  
Infrared Absorption ◽  
Lattice Site ◽  
Host Lattice ◽  
Impurity Molecule ◽  
Infrared Absorption Band ◽  
Previous Assignment ◽  
Solid Argon ◽  
Phonon Transition

The fundamental infrared absorption band of H2(D2) has been studied in the dilute solid solutions H2–Kr and D2–Ar, and the results are compared with previous data for H2–Ar. The spectrum consists of combination tones of molecular and lattice transitions; the lattice transition frequencies are (112, 22), (106, 16), and (79, 22) cm−1 for H2–Ar, H2–Kr, and D2–Ar, respectively. The previous assignment of the intense higher-frequency transition to the localized vibration of the impurity molecule on a substitutional lattice site is confirmed. The weaker lower-frequency transition is evidently due to an impurity-induced phonon transition of the host lattice.

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