Dong Dong Meng

Mid-IR and Raman Spectral Properties of Clinoatacamite-Structure Basic Copper Chlorides

Basic copper chloride Cu2(OH)3Cl and Cu2(OD)3Cl polycrystalline sample were successfully synthesized in the same single phase of clinoatacamite-structure, and the latter’s mid-infrared absorption spectra (4000-400cm–1) and Raman spectra (4000-95cm–1) were first, to the best of our knowledge, measured respectively by FTIR spectroscopy and Micro-Raman spectroscopy to study the corresponding relationship between their spectral properties and crystal structure. Through the comparative analysis of the four spectra we definitely assign or tentatively suggest the vibration modes of OH/D groups in the trimeric hydrogen bond environment, (H/DO)–Cu–(OH/D), Cl–Cu–Cl. These results can be propitious to their low temperature spectral properties which must help to understand the underlying physics of their exotic geometric frustration phenomenon.

Study on Raman Spectra of the Polyacrylonitrile Iron Complex Nanofibers

We have measured the Raman spectra of all samples in the process of preparing polyacrylonitrile (PAN) iron complex nanofibers, and compared their Raman spectral characteristics, and thus gained a preliminary result for the PAN nanofibers structural changes in the different stages. Through its Raman spectral analysis and comparison we can find that the cyano group (C N) of modified PAN nanofibers disappeared while the Raman bands of C = N group appeared. For the pre-oxidized PAN nanofiber, because the D and G bands of the C = C vibration appeared in the Raman spectra, it is concluded that the PAN nanofiber has an apparent structural change. Finally, it is also found that that Fe3+ and O2- ions have formed coordination bonds in the further prepared PAN iron (Fe3+) complex nanofibers because the characteristic Raman band of Fe = O bond appears.

Mid-IR and Raman Spectral Properties of Geometrically Frustrated Atacamite Hydroxyl Copper Chloride

The mid-IR and Raman spectra of geometrically frustrated atacamite hydroxyl copper chloride are measured by FTIR spectroscopy and HR800 Raman spectroscopy, respectively. The microscopic origins of bands within the functional group and the fingerprint regions are suggested by the known crystal structure parameters. Five distinct regions involved in hydroxyl stretching, overtones, hydroxyl deformation, Cu-O stretching, O–Cu–O symmetric stretching and O–Cu–O bending modes, pyramid-structure Cl≡Cu3 vibration modes, lattice modes, respectively.

More than Four Subtypes of Trimeric Hydrogen Bonds in Hydroxyl Halides

Through ten years physical investigation on the geometrically frustrated coordination compound series basic (hydroxyl and deuteroxyl) transition-metal halides M2(OH/D)3X (M=Mn, Fe, Co, Ni and Cu; X=Cl, Br and I), we have determined the existence of four crystal structures, whose space groups belong to Nos. 11, 14, 62 and 166, respectively, in this series till now. After studying their Raman spectra, we firmly believe that a nonnegligible hydrogen bond (H-bond) exists in every material. Considering carefully their local lattice environments of the basic groups, we find a new kind, to the best of our knowledge, of H-bond [(OH)3···M] and nominate it as the trimeric H-bond, and further confirm three types of symmetric structures, which have totally four subtypes of trimeric H-bonds so far. More two subtypes are predicted to exist in nature. This result may provide a new interesting subject for quantum chemists and material physicists.

Low Temperature Raman Spectroscopic Study on γ-Cu2(OH)3Cl

The low temperature (T) Raman spectroscopic study on the geometrically frustrated clinoatacamite γ-Cu2(OH)3Cl is reported. By measuring the T-dependent spectral profiles and representative modes, we have obtained auxiliary evidence of successive magnetic transitions near Tc1 =18.1 K and Tc2 =6.4 K determined accurately by the magnetic experiments in the Raman band frequencies and peak widths of the representative modes for magnetic research conclusions and observed a pronounced Raman spectroscopy background featuring a broad continuum at all Ts. A quantitative analysis reveals spin fluctuations on a picosecond time scale in the intermediate phase.

Multiformality of 1st, 2nd and 3rd-order Subschemes of Four-Level Optical Quantum Coherence Systems

Many quantum optical and optoelectronic achievements have been obtained by using quantum coherence effects occurred in four-level quantum systems. Here we report a systemic study on the 1st, 2nd and 3rd order subschemes of the four-level scheme with the aid of Boolean algebra, and find 7 1st order subschemes and 53 2nd order subschemes in total. Further it is found that 472 3rd-order subschemes may appear in the realistic optical quantum coherence experiments when the applied lasers are distinguished only by the strong and weak field intensities.

Spectral Properties of Alpha-Cu2(OH/D)3Br at Room Temperature

The newly identified magnetic geometric frustration material-botallackite-structure deuteroxyl copper bromide α-Cu2(OD)3Br sample was successfully synthesized in the same single phase (polycrystalline) as the H-isotope substituted sample of α-Cu2(OH)3Br, and its IR (4000-400 cm–1) absorption and Raman (4000-95 cm–1) spectra at room temperature are first, to the best of our knowledge, measured to study the corresponding relationship between these iso-structural compounds. Through the comparative analysis with those of α-Cu2(OH)3Br reported previously, we definitely assign or tentatively suggest their vibration modes according to the result of the factor group analysis.

Raman Band Redshifting of α-Cu2(OH)3Cl with Decreasing the Temperature

Raman spectra of the magnetic geometric frustration material – the botallackite-structure α-Cu2(OH)3Cl polycrystalline sample were measured down to liquid N2 temperature. It is found that the hydroxyl stretching bands shift abnormally according to the lattice thermal expansion effect of normal materials, i.e., they redshift with decreasing the sample temperature (negative thermal expansion) using liquid N2 cooling while other bands blueshift. This abnormality was also confirmed by observing the band-shifting caused by local laser heating effect using different laser powers, and can be qualitatively explained by checking the local hydroxyl environment with a trimeric hydrogen bond.

Raman Spectral Properties of β-Co2(OH)3Cl down to the Liquid Nitrogen Temperature

Raman spectra of the geometrically frustrated material sample β-Co2(OH)3Cl have first, to the best of our knowledge, been measured down to liquid nitrogen temperature using the experimental conditions of 10X-objective @ 60 mW and 50X-objective @ 5 mW, respectively. It is found that most Raman bands blueshift with decreasing the sample temperature, agreeing with the thermal expansion effect of common materials, but the Raman spectra from different experimental conditions are slightly different with each other at same temperatures. The difference between them has been explained by the local laser heating effect.

Mid-IR and Raman Spectral Properties of Hydroxyl/Deuteroxyl Cobalt Chlorides

The geometrically frustrated material-deuteroxyl cobalt chlorides Co2(OD)3Cl sample was first, to the best of our knowledge, successfully synthesized in the same single phase as the famous Co2(OH)3Cl, and their mid-infrared absorption spectra (4000-400cm–1) and Raman spectra (4000-95 cm–1) are first, to the best of our knowledge, measured respectively by FTIR spectroscopy and Micro-Raman spectroscopy to study the corresponding relationship between their spectral properties and crystal structure. Through the comparative analysis of the four spectra we definitely assign or tentatively suggest the vibration modes of hydroxyl/deuteroxyl groups in the trimeric hydrogen bond environment, (OH/D)–Co–(OH/D), and (H/D3···Cl)–Co–(Cl···H/D3). These results can be propitious to the low temperature spectral properties of Co2(OH)3Cl and Co2(OD)3Cl which must help to understand the underlying physics of their exotic geometric frustration phenomenon.