Collision-induced absorption in the fundamental band of nitrogen gas

1987 ◽  
Vol 65 (12) ◽  
pp. 1629-1635 ◽  
Author(s):  
C. G. Joslin
Keyword(s):  
Single Molecule ◽  
Intermolecular Potential ◽  
Substantial Contribution ◽  
Spectral Profile ◽  
Nitrogen Gas ◽  
Spectral Moments ◽  
Anisotropic Component ◽  
Vibration Rotation ◽  
Small Anisotropy ◽  
Good Agreement

Compressed nitrogen gas absorbs weakly in the vicinity of its vibrational fundamental frequency (ωvib = 2330 cm−1), with an intensity proportional to the square of the density. This absorption arises through vibrational modulation of the quadrupole-induced collisional dipole moment of a pair of N2 molecules. By neglecting the small anisotropy in the N2 intermolecular potential, we represent the spectral profile as the convolution of a single-molecule vibration–rotation band with a two-molecule translational component. Information theory is used to estimate the "least biased" form for the latter, based on our knowledge of its first four nonvanishing spectral moments. Our theory contains no adjustable parameters, yet yields results in good agreement with experiment. Our analysis shows that the anisotropic component of the molecular polarizability makes a fairly substantial contribution, about 12%, to the spectral intensity.

Far-infrared absorption in liquid nitrogen: a theoretical study

1985 ◽  
Vol 63 (1) ◽  
pp. 76-83 ◽  
Author(s):  
C. G. Joslin ◽  
S. Singh ◽  
C. G. Gray
Keyword(s):  
Liquid Nitrogen ◽  
Single Molecule ◽  
Theoretical Study ◽  
Far Infrared ◽  
Intermolecular Potential ◽  
Line Shapes ◽  
Absolute Intensities ◽  
Induction Mechanism ◽  
Rotation Spectrum ◽  
Small Anisotropy

We present a simple theory of the far-infrared collision-induced absorption spectrum of liquid nitrogen. Assuming a quadrupolar induction mechanism, and neglecting the small anisotropy in the N2 intermolecular potential, we represent the spectral profile as the convolution of a single-molecule free-rotation spectrum with an intermolecular translational component. Information theory is used to estimate the least-biased form for the latter, based on our knowledge of its zeroth and second spectral moments (the calculation of M0tr and M2tr is illustrated in the Appendix). In this way we avoid the need to make questionable assumptions about the system dynamics. Our theory contains no adjustable parameters, yet the computed line shapes are in excellent agreement with the available experimental data. Absolute intensities are underestimated by about 40%.

Enhanced-Fluorescence of a Dye on DNA- assembled Gold Nano-Dimers Discriminated by Lifetime Correlation Spectroscopy

2017 ◽  
Author(s):  
Pedro M. R. Paulo ◽  
David Botequim ◽  
Agnieszka Jóskowiak ◽  
Sofia Martins ◽  
Duarte M. F. Prazeres ◽  
...  
Keyword(s):  
Single Molecule ◽  
Fluorescence Emission ◽  
Directed Assembly ◽  
Plasmon Mode ◽  
Correlation Spectroscopy ◽  
Enhanced Fluorescence ◽  
Detection Volume ◽  
Relaxation Component ◽  
Good Agreement ◽  
Confocal Detection

<div> <div> <div> <p>We have employed DNA-directed assembly to prepare dimers of gold nanoparticles and used their longitudinally coupled plasmon mode to enhance the fluorescence emission of an organic red-emitting dye, Atto-655. The plasmon- enhanced fluorescence of this dye using dimers of 80 nm particles was measured at single molecule detection level. The top enhancement factors were above 1000-fold in 71% of the dimers within a total of 32 dimers measured, and, in some cases, they reached almost 4000-fold, in good agreement with model simulations. Additionally, fluorescence lifetime correlation analysis enabled the separation of enhanced from non-enhanced emission simultaneously collected in our confocal detection volume. This approach allowed us to recover a short relaxation component exclusive to enhanced emission that is attributed to the interaction of the dye with DNA in the interparticle gaps. </p> </div> </div> </div>

VIBRATIONAL FREQUENCY PERTURBATIONS IN THE RAMAN SPECTRUM OF COMPRESSED GASEOUS HYDROGEN

1964 ◽  
Vol 42 (6) ◽  
pp. 1058-1069 ◽  
Author(s):  
A. D. May ◽  
G. Varghese ◽  
J. C. Stryland ◽  
H. L. Welsh
Keyword(s):  
Raman Band ◽  
Intermolecular Forces ◽  
Hydrogen Gas ◽  
High Spectral Resolution ◽  
Intermolecular Potential ◽  
Dispersion Forces ◽  
Frequency Shifts ◽  
Linear Coefficient ◽  
Relative Population ◽  
Good Agreement

The frequencies of the Q(J) lines of the fundamental Raman band of compressed hydrogen gas were measured with high spectral resolution for a series of densities from 25 to 400 Amagat units at 300 °K and 85 °K. The frequency shifts are expressed as a power series in the gas density. The linear coefficient at a given temperature has the form aJ = ai + ae(nJ/n), where ai, constant for all the Q lines, can be interpreted in terms of isotropic intermolecular forces, and ae(nJ/n), proportional to the relative population of the initial J level, arises from the inphase coupled oscillation of pairs of molecules. The temperature variation of ai is analyzed on the basis of the Lennard-Jones intermolecular potential and the molecular pair distribution function. The repulsive overlap forces and the attractive dispersion forces give, respectively, positive and negative contributions to ai, which can be characterized by the empirical parameters Krep and Katt. The values of Katt and ae are in good agreement with calculations based on the polarizability model of the dispersion forces. The relation of the results to the Raman frequency shifts in solid hydrogen is discussed.

Isotopic Thermal Diffusion Factors for Helium and Neon at Low Temperatures

1963 ◽  
Vol 18 (2) ◽  
pp. 242-245 ◽  
Author(s):  
W. W. Watson ◽  
A. J. Howard ◽  
N. E. Miller ◽  
R. M. Shiffrin
Keyword(s):  
Thermal Diffusion ◽  
Low Temperatures ◽  
Quantum Corrections ◽  
Intermolecular Potential ◽  
De Vries ◽  
Lower Temperature ◽  
Improved Accuracy ◽  
Good Agreement

With an all-metal “swing separator” having unique features, thermal diffusion factors αT for He3/He4 and Ne20Ne22 have been measured with improved accuracy down to average gas temperatures T̅=136°K. For helium αT is 0.0696 ± 0.0010 at 136°K, dropping gradually to 0.0651 ±0.0010 at 313°K. These data, plus measurements by Van der Valk and de Vries at somewhat higher temperatures, agree best with values predicted by an exp-six intermolecular potential with ε/k=9.16 and α=12.7. We are extending these helium measurements down to T=4°K for the lower temperature, to detect if possible quantum corrections to the intermolecular potential. For neon αT increases from 0.0166 ± 0.0010 at 136°K to 0.0233 ± 0.0020 at 310°K, considerably higher than our previously reported values. These T. D. factors for neon are in good agreement with values calculated from an exp-six potential with ε/k = 46.0 ± 0.6 and α=13.

Defining soil macrofauna composition and activity for biopedological studies - A case study on two soils in the Western Australian wheat belt

Soil Research ◽  
1993 ◽  
Vol 31 (1) ◽  
pp. 83 ◽  
Author(s):  
LAL Debruyn
Keyword(s):  
Substantial Contribution ◽  
Resident Species ◽  
Pitfall Trapping ◽  
Soil Macrofauna ◽  
Major Species ◽  
Australian Wheat ◽  
Species Mapping ◽  
Western Australian ◽  
Good Agreement

In Durokoppin reserve and surrounding farmland, part of the central wheatbelt region, pitfall trapping and mapping of soil macrofauna activity were used to define the extent of soil macrofauna activity in these two environments. This type of study is a necessary precursor to determining the significance of certain invertebrate activity in soil modification in these habitats. The relative merits of the two techniques in determining the extent of soil macrofauna activity is assessed. The soil macrofauna groups identified by mapping and pitfall trapping as making a substantial contribution (in terms of relative abundance and activity) in all habitats were, in descending order, ants, spiders and scorpions (wandoo woodland only). In general there was good agreement between the two techniques in identifying the major species and trends in species composition between habitats, but mapping failed to identify the rare or cryptic species. Mapping more accurately identified the resident species in each habitat compared with pitfall trapping. Pitfall trapping data indicated that foraging activity of most soil macrofauna was depressed over winter, except for beetles, and was higher in the spring and summer sampling periods. However, mapping revealed a more constant level of soil macrofauna activity, especially for ant nests. It is argued that the two approaches complement one another and that each has value in interpreting the effects of soil macrofauna activity on soil properties in further studies. The discussion is based on the results of a study carried out in the Kellerberrin area of Western Australia.

The spectroscopy of van der Waals molecules

1976 ◽  
Vol 54 (5) ◽  
pp. 487-504 ◽  
Author(s):  
George E. Ewing
Keyword(s):  
Energy Levels ◽  
Van Der Waals ◽  
Electronic Spectroscopy ◽  
Spectroscopic Constants ◽  
Intermolecular Potential ◽  
Interatomic Potentials ◽  
Strongly Coupled ◽  
Van Der Waals Molecules ◽  
Angular Momenta ◽  
Vibration Rotation

The recent spectroscopy of van der Waals molecules is reviewed. Examples are presented from radio-frequency, microwave, Raman, infrared, and electronic spectroscopy. Diatomic van der Waals molecules (e.g. Ne2, Ar2, Kr2, Mg2) reveal a manifold of closely spaced vibration–rotation levels consistent with the small dissociation energies which are orders of magnitude less than for ordinary chemically bonded molecules. The (isotropic) interatomic potentials which define these molecules may be evaluated from their energy levels. Polyatomic van der Waals molecules (e.g. H2–Ar, FCl–Ar, (H2)2, (O2)2, (CO2)2) are classified according to the strength of the (anisotropic) intermolecular potential which tends to define their geometry. This classification depends on the nature of the coupling of the rotational angular momenta and leads to a labeling of the complexes as free rotor, weakly coupled, strongly coupled, or semirigid. The spectroscopic constants which are determined from the energy levels of diatomic and polyatomic van der Waals molecules can be used to better understand the intermolecular bonding which holds these molecules together.

Rotational temperature profiles of shock waves in diatomic gases

1971 ◽  
Vol 49 (2) ◽  
pp. 337-351 ◽  
Author(s):  
A. K. Macpherson
Keyword(s):  
Shock Waves ◽  
Rotational Temperature ◽  
Rotational Velocity ◽  
Three Dimensional ◽  
Intermolecular Potential ◽  
Collision Dynamics ◽  
Density Profiles ◽  
Frequency Distributions ◽  
Dimensional Approximation ◽  
Good Agreement

The variation of the translational temperature, rotational temperature, and density through shock waves in oxygen and nitrogen was studied using classical laws of mechanics and a Monte Carlo scheme. The collision dynamics were calculated using an intermolecular potential by Parker with both a two-dimensional approximation and the full three-dimensional calculations. The rotational velocity frequency distributions were also calculated. The average number of collisions a molecule will experience a t various stages passing through a shock wave were found and plotted with the temperature and density profiles. The nitrogen results were compared with experimental results and good agreement was found. This also provided a method for giving a first approximation to the three-dimensional intermolecular potential.

Laser Magnetic Resonance Spectra of 14NO2 and 15NO2 near 1600 cm−1

1975 ◽  
Vol 53 (19) ◽  
pp. 1929-1938 ◽  
Author(s):  
S. M. Freund ◽  
J. T. Hougen ◽  
W. J. Lafferty
Keyword(s):  
Magnetic Resonance ◽  
Spin Rotation ◽  
Zero Field ◽  
Co Laser ◽  
Wave Numbers ◽  
Vibration Rotation ◽  
Laser Magnetic Resonance ◽  
Stable Molecule ◽  
Transition Wave ◽  
Good Agreement

Two laser magnetic resonance patterns for 14NO2 and six patterns for 15NO2, observed using six CO laser transitions, have been analyzed to yield spin corrected zero-field vibration–rotation transition wave numbers and zero-field spin–rotation splittings. The 14NO2 results are in good agreement with results obtained from conventional infrared grating studies. The 15NO2 results allow new values of ν0 = 1582.107 ± 0.008, A′ − A″ = −0.2116 ± 0.0011, and DK′ − DK″ = −1.39 ± 0.20 × 10−4 cm−1 to be determined for the ν3 fundamental of that molecule (errors are 3 standard deviations). Two spectral figures and a list of assigned Zeeman lines are presented to permit using this stable molecule as an aid in adjusting newly constructed instruments. Closed form approximate intensity expressions are given for Zeeman transitions of the type observed in this work, i.e., for sharp partially spin forbidden Zeeman transitions in A type bands of near prolate asymmetric rotors.

Enhanced-Fluorescence of a Dye on DNA- assembled Gold Nano-Dimers Discriminated by Lifetime Correlation Spectroscopy

2017 ◽  
Author(s):  
Pedro M. R. Paulo ◽  
David Botequim ◽  
Agnieszka Jóskowiak ◽  
Sofia Martins ◽  
Duarte M. F. Prazeres ◽  
...  
Keyword(s):  
Single Molecule ◽  
Fluorescence Emission ◽  
Directed Assembly ◽  
Plasmon Mode ◽  
Correlation Spectroscopy ◽  
Enhanced Fluorescence ◽  
Detection Volume ◽  
Relaxation Component ◽  
Good Agreement ◽  
Confocal Detection

<div> <div> <div> <p>We have employed DNA-directed assembly to prepare dimers of gold nanoparticles and used their longitudinally coupled plasmon mode to enhance the fluorescence emission of an organic red-emitting dye, Atto-655. The plasmon- enhanced fluorescence of this dye using dimers of 80 nm particles was measured at single molecule detection level. The top enhancement factors were above 1000-fold in 71% of the dimers within a total of 32 dimers measured, and, in some cases, they reached almost 4000-fold, in good agreement with model simulations. Additionally, fluorescence lifetime correlation analysis enabled the separation of enhanced from non-enhanced emission simultaneously collected in our confocal detection volume. This approach allowed us to recover a short relaxation component exclusive to enhanced emission that is attributed to the interaction of the dye with DNA in the interparticle gaps. </p> </div> </div> </div>

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