Related Experiment Video
Updated: Aug 3, 2026
08:48
Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment
Published on: November 9, 2015
The Rotational Spectrum of Ar-SiH(4) and Ar-SiD(4)
1Department of Applied Chemistry, Kanagawa Institute of Technology, 1030 Shimo-ogino, Atsugi, Kanagawa, 243-0292, Japan
Journal of Molecular Spectroscopy
|November 30, 1999
Summary
This study measured microwave spectra of argon-silane complexes, revealing detailed rotational structures and determining the electric dipole moment of argon-silicon tetrahydride. These findings enhance our understanding of molecular interactions.
Area of Science:
- Molecular Spectroscopy
- Physical Chemistry
- Quantum Mechanics
Background:
- Understanding the van der Waals interactions in weakly bound complexes like argon-silane is crucial for theoretical and experimental chemistry.
- Previous studies have utilized infrared spectroscopy, but microwave spectroscopy offers higher precision for rotational analysis.
Purpose of the Study:
- To investigate the rotational dynamics and intermolecular forces in argon-silane (Ar-SiH4) and its isotopologues using microwave spectroscopy.
- To precisely determine spectroscopic constants and the electric dipole moment of the Ar-SiH4 complex.
Main Methods:
- Pulsed molecular beam Fourier transform microwave spectroscopy was employed to record spectra in the 9-24 GHz range.
- Rotational transitions (J=3←2 to J=7←6) for K=0 and K=1 states were measured for Ar-(28)SiH4, Ar-(29)SiH4, Ar-(30)SiH4, and Ar-(28)SiD4.
- Analysis of the Stark effect on E-state transitions was performed to determine the electric dipole moment.
Main Results:
- Observed and assigned various rotational progressions, including A, F, and E symmetry states, for argon-silane isotopologues.
- Determined accurate rotational and centrifugal distortion constants for Ar-(28)SiH4 and Ar-(28)SiD4.
- Measured an electric dipole moment of 9.24(8) x 10⁻³² C·m (0.0277(2) D) for the Ar-SiH4 complex.
Conclusions:
- The microwave spectra provide detailed insights into the structure and dynamics of the Ar-SiH4 van der Waals complex.
- The determined spectroscopic constants align well with infrared data, validating the microwave measurements.
- The measured dipole moment offers a quantitative measure of the charge distribution and interaction within the complex.
Related Concept Videos
03:24Hybridization of Atomic Orbitals I
The mathematical expression known as the wave function, ψ, contains information about each orbital and the wavelike properties of electrons in an isolated atom. When atoms are bound together in a molecule, the wave functions combine to produce new mathematical descriptions that have different shapes. This process of combining the wave functions for atomic orbitals is called hybridization and is mathematically accomplished by the linear combination of atomic orbitals. The new orbitals that...
02:30Chirality at Nitrogen, Phosphorus, and Sulfur
Chirality is most prevalent in carbon-based tetrahedral compounds, but this important facet of molecular symmetry extends to sp3-hybridized nitrogen, phosphorus and sulfur centers, including trivalent molecules with lone pairs. Here, the lone pair behaves as a functional group in addition to the other three substituents to form an analogous tetrahedral center that can be chiral.
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
01:19IR Spectrum
When infrared (IR) radiation passes through a molecule, the bonds stretch or bend by absorbing the radiation. This absorption creates the molecule's absorption spectrum, which is the plot of its percentage transmittance versus wavenumber.
Transmittance is defined as the ratio of the radiant power passing through a sample to that from the radiation's source. Multiplying the transmittance by 100 gives the percent transmittance (%T), which varies between 100% (no absorption) and 0% (complete...
Transmittance is defined as the ratio of the radiant power passing through a sample to that from the radiation's source. Multiplying the transmittance by 100 gives the percent transmittance (%T), which varies between 100% (no absorption) and 0% (complete...
01:08IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single stretching vibration...
01:24IR Spectroscopy: Molecular Vibration Overview
When Infrared (IR) radiation passes through a covalently bonded molecule, the bonds transition from lower to higher vibrational levels. The fundamental vibrational motions that result in infrared absorption can be classified as stretching or bending vibrations.
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
01:21IR Absorption Frequency: Hybridization
Hydrocarbons such as alkanes, alkenes, and alkynes show characteristic C–H stretching absorption bands. These IR stretching frequencies depend on the hybridization of the involved carbon atom and can be explained in terms of the s character of each hybridized atomic orbital.
Among the sp, sp2, and sp3 hybridized orbitals, sp orbitals have the maximum s character (50%). Consequently, the electrons are held more closely to the nucleus, resulting in stronger and shorter C–H bonds that stretch at a...
Among the sp, sp2, and sp3 hybridized orbitals, sp orbitals have the maximum s character (50%). Consequently, the electrons are held more closely to the nucleus, resulting in stronger and shorter C–H bonds that stretch at a...