Department of physics

C2. Condensed Matter (Theory) Group:

Solid state Physics is one of the thrust areas recognised by UGC under CAS. The computational activities of this group involve carbon nano-materials which form currently important area of research. On-going work involves study of properties of carbon nanotubes and clusters of metals and semiconductors using various techniques. We also study anharmonic properties especially in the context of shock wave propagation in materials.

A large number of Ph.D.s have been granted in these areas and a significant number of M.Sc. (project) and M. Tech. (Nano-science and nano-technology) student are working with this group.

Current Activities

The last decade has seen a huge interest in the properties of matter at nanometer scale. Today it is practically (and arguably) the most active area of research in Physical sciences.

Our work mainly consist of predicting/ confirming the structure, dynamics and thermal properties of various carbon materials and other nanosystems such as metal clusters, BN Nanotubes etc., using potential models. We are also using proprietary software to determine electronic structure of these systems. Beginnings have been made in nanofluidics.

Properties of Clusters – Calculations

We are exploring structure and electronic properties of endohedral fullerenes and carbon nanotubes doped with different metals, transition metal and magnetic atoms and their clusters. Apart from this dilute magnetic semiconductors and oxide semiconductors are also studied for their application as spintronic materials. We use various Packages, all using Density Functional schemes. The systems investigated are gold nanocages, endohedral buckyballs and gold clusters with Si doping. All these systems have projected uses in nano-electronics. Two important results have been obtained so far -- the Au-Si system is shown to have a far greater tendency to form monatomic sheets as compared to pure gold, which may have relevance for nano-electronica; the C60 buckyball ia capable of accommodating a large number of N atoms in single bonded configuration, which may have relevance for energy storage material.

Single atom gold chains, which are actually seen to form under an atomic force microscope, have been investigated by an atom- atom potential method using simple molecular mechanics methods. Calculations not only match experimental findings, but predict a few interesting mechanical properties (plasticity) of such monatomic Au nanowires.

Our computational efforts are going to see a thrust in electronic structure calculations. This requires cluster computing for which the system needs to be acquired. We also need to do molecular dynamics simulations for which software has to be obtained. All of these are being planned to be included in regular teaching courses (e.g., 'simulation' course under NSNT, 'programming' course under M.Sc. and special paper on nanomaterials for M.Sc. Physics students).

(D) Molecular Spectroscopy Group:

The Molecular Spectroscopy group is working in the following areas:

1. 
   Porphyrins, which are biologically important molecule and found in heamoglobin, myoglobin, and cytochromes etc. Chlorophyll and Vitamin B₁₂ are also related compounds. We are studying chemical and photo-induced electron transfer processes in porphyrins and their gas sensing properties with the help of vibrational spectroscopic techniques and density functional theory calculations.
   
2. 
   Phthalocyanines: These are organic semi conductors and have many practical applications. We are studying their volatile organic chemical sensing properties by spectroscopic techniques and density functional theory.
   

Initially, we studied the effect of pyridine on the geometrical structure and vibrations of zinc phthalocyanine in order to understand the possible interactions of organic vapours molecules with the phthalocyanine molecules. We have used density functional theory calculations and infrared absorption spectroscopy for this purpose. X-ray diffraction pattern was also recorded in the absence and presence of pyridine. In the presence of pyridine phase of the crystalline zinc phthalocyanine changes from b to a. Some infrared bands show changes in their positions and/or intensities. These changes have been interpreted on the basis of coordination of the pyridine molecule with the central zinc ion. Coordinated pyridine transfers some of its charge to the p electron system of the phthalocyanine ring through zinc ion. Pyridine molecule also distorts the phthalocyanine molecule by pulling zinc ion out of the phthalocyanine plane. Density functional theory also confirms the ligation of pyridine molecule at the fifth coordination site of the central metal ion.

Next, we have studied zinc phthalocyanine thin film and chemical analyte interactions by density functional theory and vibrational techniques. For this purpose, thin films of zinc phthalocyanine were deposited on KBr and glass substrates by the thermal evaporation method and characterized by the x-ray diffraction, optical, infrared and Raman techniques. The observed x-ray diffraction and infrared absorption spectra of as-deposited thin films

suggested the presence of an a crystalline phase. Infrared and Raman spectra of thin films after exposure to vapours of ammonia and methanol had also been recorded. Shifts in the position of some IR and Raman bands in the spectra of exposed films were observed. Some bands also showed changes in their intensity on exposure. Increased charge on the phthalocyanine ring and out-of-plane distortion of the core due to interaction between zinc phthalocyanine and vapour molecules involving the fifth coordination site of the central metal ion might be responsible for the band shifts. Changes in the intensity of bands were

interpreted in terms of the lowering of molecular symmetry from D4h to C4v due to doming of the core. Molecular parameters and Mulliken atomic charges of zinc phthalocyanine and its complexes with methanol and ammonia had been calculated from density functional theory. The binding energy of the complexes had also been calculated. Calculated values of the energy for different complexes suggested that axially coordinated vapour molecules formed the most stable complex. Calculated Mulliken atomic charges showed net charge transfer from vapour molecules to the phthalocyanine ring for the most stable complex.

We have also studied the effects of chemical vapours on the vibrational spectra of nickel phthalocyanine thin films experimentally and theoretically by density functional theory. Effects of chemical vapours on the Raman and infrared absorption spectra of a crystalline nickel phthalocyanine thin films were reported. Transmission electron micrograph of the thin films suggested presence of nano-sized particles of nickel phthalocyanine in the thin film. Some vibrational bands showed changes in their positions and/or intensities on exposure of thin films with chemical vapours. These changes were interpreted on the basis of interactions of the vapours molecule with the central nickel ion and other peripheral atoms of the phthalocyanine ring. Density functional theory calculations were also carried out to determine the probable geometric structures of the complexes of vapour and phthalocyanine molecules. Calculated geometric structures showed in-plane and out-of-plane distortions in the phthalocyanine molecule. Calculations further suggested charge transfer between vapour

and phthalocyanine molecules. In contrast to zinc phthalocyanine, this molecule can form six coordinated species with vapour molecules.

We have also studied the sensing mechanism of zinc tetraphenylporphine (ZnTPP) towards the methanol, pyridine, diethylamine, dichloromethane, acetonitrile, bromine and NO2 vapours. We deposited thin films of ZnTPP and recorded the resonance Raman and infrared absorption spectra of thin films before and after exposure with diethyl amine/methanol vapours. Positions of some vibrational bands show detectable change on exposure. Changes

in the intensity of some vibrational bands of the thin films have also been observed on exposure. Coordination of vapours molecules at the zinc ion and subsequent charge transfer are responsible for the shift in the vibrational bands. Density functional theory calculations have been carried out to determine the probable geometric structures of the porphyrin-vapour complexes. Calculated geometric structures show in-plane and out-of-plane distortions in the porphyrin macrocycle. Calculations also result in charge transfer between vapour and porphyrin molecules.

3. 
   Laser dyes: We are also interested in some laser dyes of xanthene family and coumarins. Presently, we are studying the salvation dynamics of these dyes with the help of vibrational spectroscopic techniques and density function theory calculations.
   
4. 
   We are also working on the vibrational dynamics of some potential radio protective antioxidant and radical reactions.
   

(E) Mass Spectrometry and Geochronology Group:

Group Members:

The group are carrying out the Rb-Sr Isotopic and Geochronological investigations on the granitic and gneissic rocks of the Himalaya. The granitic and gneissic rocks have preserved in them episodes of magmatic and metamorphic activities which occurred over a great span of time from Precambrian to recent, including Himalayan Orogeny. It is not possible to establish and define precisely most of these events by routine geological methods such as the nature of xenoliths present, field relationship with the country rocks, petrographical similarities, structural trends, grade of metamorphism etc. The Rb-Sr isotopic and geochronological studies provide an invaluable tool to unravel many important events such as the ages of some igneous and metamorphic rocks, petrogenetic history, metamorphism, mineral ages, rate of cooling etc. The Rb-Sr age data could be used for correlation of the rocks under study with their possible equivalents in different parts of the Himalaya and also in the Peninsular India.

Highlights / achievements of Research Work done by the group : The group has published a number of Rb-Sr isotopic ages for the Himalaya granites and gneisses which provided a new dimension to the interpretation of geological events and completely changed the old conjectural geological thinking about these rocks. Thus when Jaeger et al, 1971 for the first time reported the age of 517± 100 M.Y. for the Mandi granite, it was taken with criticism as most of the geologists at that time considered it to be of Tertiary age (<65M.Y.). When the same age data was confirmed by scientists working in foreign laboratories, it changed the geological thinking. The work of the group led to the recognition of the following main periods of magmatic activity based on Rb-Sr whole rock isotopic ages of the granites and gneisses:

1. 
   Ages around 2000 M.Y.
   

The granitic and gneissic rocks of this age group have been reported from Munsiari, Askot, Tawaghat, Namik, Dhakuri, Joshimath-Guptkashi, Hanuman Chatti, Rihee-Gangi, Bhatwari and Naitwar areas of Kamaun-Garhwal Himalaya; Wangtu, Bandal and Baragaon of Himachal Himalaya and Shasho and Lopara Kashmir Himalaya.

b). Ages around 1500 M.Y.

The granites and gneisses of this age group have been obtained from Mayali, Maithana, Chandrapuri, Chamoli and Amritpur areas of Kumaun Himalaya; Baragaon and Nirath of Himachal Himalaya and Kalaktang of Arunachal Himalaya.

2. 
   Ages around 1200 M.Y.
   

The rocks of the age group of about 1200 M.Y. include Koidal gneiss, Gwaldom granite, Baijnath-Therali gneiss, Ramgarh gneiss and Amritpur grey granite of Kumaun Himalaya and Bandal granite and Chor granitic gneiss of Himachal Himalaya.

3. 
   Ages around 500 M.Y.
   

This is the most widely spread age group. The granites and gneisses of the age group of about 500 M.Y. have been reported from Doda and Kishtwar- Thathari areas of Kashmir Himalaya; Mandi,Karsog, Sarangi- Ranga Thach N.E. of Manikaran, Manali, Koksar, Chhotadara, Jaspa, Dalhousie, Akpa, Rakcham-Chitkul-Sangla, Chor and Khadrala areas of Himachal Himalaya and Ranikhet, Champawat, Dudatoli, Vaikrita group north of Tawaghat and Harsil areas of Kumaun Himalaya.

e) Ages around 350 M.Y.

The granitic and gneissic rocks of this age group have been obtained from Dalhousie area of Himachal Himalaya and Masi, Lansdowne and Almora areas of Kumaun Himalaya.

Presently we are carrying out Rb-Sr Isotopic and Geochronological studies on the biotite and muscovite separated from the granitic and gneissic rocks of the following areas from Himachal Himalaya:

1. Manali, Chhotadara and Jaspa

2. Wangtu and Tapri

3. Rakcham, Karcham and Chitkul

This study will provide the

• 
  Thermal history
  
• 
  Rate of uplift
  
• 
  Other geological aspect of these areas.
  

We are also carrying out Systematic Rb-Sr isotopic studies on the water samples of hot springs from different areas of Himachal Himalaya and rivers Satluj, Baspa, Beas and their tributories and nullahs. This study will give information about

• 
  The source material of the water
  
• 
  Sr isotopic constituents
  
• 
  Mineral explorations
  
• 
  Contribution of Satluj, Baspa and Beas rivers to the oceanic Strontium budget
  
• 
  Explanation to the increasing ⁸⁷Sr/ ⁸⁶Sr ratio in ocean water even beyond global values
  
• 
  Information about basement rocks of hot water sources and the presence of radioactive material.
  

3. List of Publications (2008 onwards)

Experimental High Energy Group & Heavy Ion Group

(CMS, D0, BELLE, L3, ZEUS Experiments)

1. 
   Search for anomalous $Wtb$ couplings in single top quark production in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV, By D0 Collaboration (Victor Mukhamedovich Abazov, S. B. Beri, V. Bhatnagar et al.). Phys.Lett. B708 (2012) 21-26.
   
2. 
   Measurement of the relative branching ratio of $B^0_s to J/\psi f_{0}(980) \to B_{s}^{0} \to J/\psi \phi$ By D0 Collaboration (Victor Mukhamedovich Abazov, S. B. Beri, V. Bhatnagar et al.).
   Phys.Rev. D85 (2012) 011103.
   
3. 
   Evidence for spin correlation in $t\bar{t}$ production
   By D0 Collaboration (Victor Mukhamedovich Abazov, S. B. Beri, V. Bhatnagar et al.).
   Phys.Rev.Lett. 108 (2012) 032004.
   
4. 
   Measurement of the weak mixing angle with the Drell-Yan process in proton-proton collisions at the LHC, By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.). Phys.Rev. D84 (2011) 112002.
   
5. 
   Measurement of energy flow at large pseudorapidities in pp collisions at sqrt(s) = 0.9 and 7 TeV
   By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
   JHEP 1111 (2011) 148.
   
6. 
   Search for a Vector-like Quark with Charge 2/3 in t + Z Events from pp Collisions at sqrt(s) = 7 TeV By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
   Phys.Rev.Lett. 107 (2011) 271802.
   
7. 
   $W\gamma$ production and limits on anomalous $WW\gamma$ couplings in $p\bar{p}$ collisions, By The D0 Collaboration (Victor Mukhamedovich Abazov, S. B. Beri, V. Bhatnagar et al.). Phys.Rev.Lett. 107 (2011) 241803.
   
8. 
   Search for Supersymmetry at the LHC in Events with Jets and Missing Transverse Energy
   By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
   Phys.Rev.Lett. 107 (2011) 221804.
   

9. 
   Measurement of the t $\bar{t} Production Cross Section in pp Collisions at 7 TeV in Lepton + Jets Events Using b-quark Jet Identification
   By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
   Phys.Rev. D84 (2011) 092004.
   
10. 
    Measurements of single top quark production cross sections and $|V_{tb}|$ in $p\bar{p} collisions at $\sqrt{s}=1.96$ TeV
    By D0 Collaboration (Victor Mukhamedovich Abazov, S. B. Beri, V. Bhatnagar et al.).
    Phys.Rev. D84 (2011) 112001.
    
11. 
    Measurement of the Differential Cross Section for Isolated Prompt Photon Production in pp Collisions at 7 TeV
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    Phys.Rev. D84 (2011) 052011.
    
12. 
    Measurement of the Drell-Yan Cross Section in pp Collisions at sqrt(s) = 7 TeV
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    JHEP 1110 (2011) 007.
    
13. 
    Search for B(s) and B to dimuon decays in pp collisions at 7 TeV
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    Phys.Rev.Lett. 107 (2011) 191802.
    
14. 
    Forward-backward asymmetry in top quark-antiquark production
    By D0 Collaboration (Victor Mukhamedovich Abazov, S. B. Beri, V. Bhatnagar et al.).
    Phys.Rev. D84 (2011) 112005.
    
15. 
    Search for Resonances in the Dijet Mass Spectrum from 7 TeV pp Collisions at CMS
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    Phys.Lett. B704 (2011) 123-142.
    
16. 
    Measurement of the Inclusive W and Z Production Cross Sections in pp Collisions at sqrt(s) = 7 TeV
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.). arXiv:1107.4789 [hep-ex].
    JHEP 1110 (2011) 132.
    
17. 
    Dependence on pseudorapidity and centrality of charged hadron production in PbPb collisions at a nucleon-nucleon centre-of-mass energy of 2.76 TeV
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    JHEP 1108 (2011) 141.
    
18. 
    Search for the standard model and a fermiophobic Higgs boson in diphoton final states
    By D0 Collaboration (V.M. Abazov, S. B. Beri, V. Bhatnagar et al.).
    Phys.Rev.Lett. 107 (2011) 151801.
    
19. 
    Determination of Jet Energy Calibration and Transverse Momentum Resolution in CMS
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    JINST 6 (2011) P11002.
    
20. 
    Search for Three-Jet Resonances in pp Collisions at sqrt(s) = 7 TeV
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    Phys.Rev.Lett. 107 (2011) 101801.
    
21. 
    Search for supersymmetry in pp collisions at sqrt(s)=7 TeV in events with a single lepton, jets, and missing transverse momentum
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    JHEP 1108 (2011) 156.
    
22. 
    Search for first generation leptoquark pair production in the electron + missing energy + jets final state, By D0 Collaboration (Victor Mukhamedovich Abazov, S. B. Beri, V. Bhatnagar et al.).
    Phys.Rev. D84 (2011) 071104.
    
23. 
    A search for excited leptons in pp Collisions at sqrt(s) = 7 TeV
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    Phys.Lett. B704 (2011) 143-162.
    
24. 
    Search for associated Higgs boson production using like charge dilepton events in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV
    By D0 Collaboration (V.M. Abazov, S. B. Beri, V. Bhatnagar et al.).
    Phys.Rev. D84 (2011) 092002.
    
25. 
    Measurement of the Underlying Event Activity at the LHC with $\sqrt{s}= 7$ TeV and Comparison with $\sqrt{s} = 0.9$ TeV
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    JHEP 1109 (2011) 109.
    
26. 
    Measurement of the anomalous like-sign dimuon charge asymmetry with 9 fb^-1 of p pbar collisions
    By D0 Collaboration (Victor Mukhamedovich Abazov, S. B. Beri, V. Bhatnagar et al.).
    Phys.Rev. D84 (2011) 052007.
    
27. 
    Precision measurement of the ratio ${\rm B}(t \to Wb)/{\rm B}(t \to Wq)$ and Extraction of $V_{tb}$
    By D0 Collaboration (V.M. Abazov, S. B. Beri, V. Bhatnagar et al.).
    Phys.Rev.Lett. 107 (2011) 121802.
    
28. 
    Search for neutral Minimal Supersymmetric Standard Model Higgs bosons decaying to tau pairs produced in association with $b$ quarks in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV
    By D0 Collaboration (Victor Mukhamedovich Abazov, S. B. Beri, V. Bhatnagar et al.).
    Phys.Rev.Lett. 107 (2011) 121801.
    
29. 
    Missing transverse energy performance of the CMS detector
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    JINST 6 (2011) P09001.
    
30. 
    Search for Higgs bosons decaying to $\tau\tau$ pairs in $p\bar {p}$ collisions at $\sqrt{s} = 1.96$ TeV, By D0 Collaboration (Victor Mukhamedovich Abazov, S. B. Beri, V. Bhatnagar et al.).
    Phys.Lett. B707 (2012) 323-329.
    
31. 
    Search for New Physics with a Mono-Jet and Missing Transverse Energy in $pp$ Collisions at $\sqrt{s} = 7$ TeV
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    Phys.Rev.Lett. 107 (2011) 201804.
    
32. 
    Search for New Physics with Jets and Missing Transverse Momentum in pp collisions at sqrt(s) = 7 TeV, By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    JHEP 1108 (2011) 155.
    
33. 
    Search for doubly-charged Higgs boson pair production in $p\bar {p}$ collisions at $\sqrt{s} = 1.96$ TeV, By D0 Collaboration (Victor Mukhamedovich Abazov, S. B. Beri, V. Bhatnagar et al.).
    Phys.Rev.Lett. 108 (2012) 021801.
    
34. 
    Measurement of the Strange B Meson Production Cross Section with J/Psi phi Decays in pp Collisions at sqrt(s) = 7 TeV
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    Phys.Rev. D84 (2011) 052008.
    

35. 
    Search for Supersymmetry in Events with b Jets and Missing Transverse Momentum at the LHC
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    JHEP 1107 (2011) 113.
    
36. 
    Measurement of the t-channel single top quark production cross section in pp collisions at sqrt(s) = 7 TeV
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    Phys.Rev.Lett. 107 (2011) 091802.
    
37. 
    Search for Light Resonances Decaying into Pairs of Muons as a Signal of New Physics
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    JHEP 1107 (2011) 098.
    
38. 
    Bounds on an anomalous dijet resonance in $W+$jets production in ppbar collisions at $\sqrt{s} =1.96$ TeV, By D0 Collaboration (V.M. Abazov, S. B. Beri, V. Bhatnagar et al.).
    Phys.Rev.Lett. 107 (2011) 011804.
    
39. 
    Direct measurement of the mass difference between top and antitop quarks
    By D0 Collaboration (Victor Mukhamedovich Abazov, S. B. Beri, V. Bhatnagar et al.).
    Phys.Rev. D84 (2011) 052005.
    
40. 
    Search for Same-Sign Top-Quark Pair Production at sqrt(s) = 7 TeV and Limits on Flavour Changing Neutral Currents in the Top Sector
    By CMS Collaboration (Serguei Chatrchyan, S.B.Beri, V.Bhatnagar, M.Kaur, J.B.Singh et al.).
    JHEP 1108 (2011) 005.
    
    
41. 
    Measurements of inclusive $W+$jets production rates as a function of jet transverse momentum in $p\bar{p}$ collisions at $\sqrt{s}=1.96$~TeV
    By D0 Collaboration (Victor Mukhamedovich Abazov, S. B. Beri, V. Bhatnagar et al.).