There is a growing realisation that small molecules exist not just in quiescent cool clouds but also in much more active astrophysical regions such as planetary nebulae and diffuse interstellar clouds. These regions often contain significant numbers of free, quasi-thermal electrons, up to 10-4 compared to molecular hydrogen. These electrons can effect chemical change and drive observable spectroscopy processes (see A.J. Lim, I. Rabadan and J. Tennyson, MNRAS, 306, 473 (1999) for example); the cross sections between electrons and molecular ions are particularly large. Additionally electron molecule collisions are important elsewhere, for example they are the main driver behind planetary aurorae and many molecular masers. Models of all these regimes require data which is largely unknown and, in many cases, cannot be determined from laboratory based measurements. Over the last two decades the UCL group has developed the UK molecular R-matrix codes to provide a first principles, quantum mechanical treatment of the collision between low energy electrons and small molecules. This code has been used to treat collisions leading to rotational excitation involving important astrophysical ions (see for example A. Faure and J. Tennyson, MNRAS, 325, 443 (2001)) and the strongly dipolar water molecule (A. Faure, J.D. Gorfinkiel and J. Tennyson, MNRAS 347, 323 (2004)). However these treatments are still very limited in their scope. Thus, for example, calculations on electron collisions with water which are important for models of water masers and cometary emissions, and will undoubtedly be needed to interpret observations from ESA's forthcoming Herschel mission, need to be extended to treat both much higher rotational levels and vibrational motion. Recent observations of molecular emissions from C-shocked regions of the ISM (Jimenez-Serra et al, ApJ 650, L135 (2007)) showed that it is possible to recover local electron densities by using electron molecule collisions calculations (this work used ones performed by the proposer). The present proposal is for a PhD student who will use the QuantemolN implementation of the UK polyatomic R- matrix code to study electron collisions with molecules of astrophysical interest such as OH and SiO. Similar electron collisions with C2, important in cometary tails and elsewhere, will also be attempted. The QuantemolN code, which will be provided by the company, is very suitable for these studies since it is an expert system which greatly increases the ease and speed with which a user can perform very technically demanding electron collision calculations. In return the student will assist the company in adding further features to this code, for example to treat rotational and vibrational excitation. Adding to the functionality of the code is a strategic aim of Quantemol. The student will be provided training in performing electron molecule collision calculations, interpreting the results and using them in astronomical models and to interpret astronomical spectra. S/he will interact with people directly observing the processes, several of whom (for example Dr J Rawlings and Dr S Viti) are at UCL. S/he will also experience working with a small start up company which gives the opportunity to be involved both in the software development and in the interaction with other users of the code. This proposal follows a highly successful CASE studentship award (now in its final year) to Mr HN Varambhia who has both QuantemolN to do studies on HCN, HNC, CO and other astrophysically important systems (Eg Varambhia et al, Electron-impact rotational excitation of HCN, HNC, DCN and DNC, MNRAS in press) which has been of immense benefit to the company by raising its scientific profile which led to new orders for the existing Quantemol-N package and interest in both Quantemol-N and Quantemol-P from both the UK and abroad.

The dynamics of quantum particles is the basis to describing the material world. Collisions between nuclei provides basic chemical reactivity, while the movements of electrons around nuclei provides the fine mechanistic details. To understand these motions we need to solve the time-dependent Schroedinger equation - a non-trivial problem for more than 3 particles that requires a huge computational effort. State-of-the art experiments using attosecond or femtosecond pulses of radiation allow us to follow the motion of these particles, but without computer simulations the results are difficult to understand. This field of research is presently undergoing a huge expansion, due to the provision of new light sources such as free electron lasers (FELs), and software needs to be developed to keep up to the new capabilities. CCPQ has two community codes (R-matrix suite, MCTDH wavepacket dynamics) to treat these processes. The results give a deep inside into the fundamental reactivity of molecules, where quantum mechanical behaviour must be considered. The interactions of anti-matter particles are also a topic of much interest, primarily due to the use of positrons in medical imaging, but also as a field of fundamental science in experiments such as the ALPHA project. Here, anti-matter particles are collided with normal matter and the different decay channels investigated. CCPQ is developing a code in collaboration with experimentalists to help understand the behaviour of these exotic sounding, but useful, particles. Going from few bodies to many-bodies introduces some of the most fascinating phenomena in physics, such as superfluidity, superconductivity and ferroelectricity. However, to directly simulate them also introduces an exponentially scaling overhead in computation effort with the system size. While usually the preserve of condensed matter systems such strongly-correlated physics, where particles behaviour collectively, are now accessible in controlled ways with cold-atoms trapped in optical lattices. This has opened up previously inaccessible coherent dynamics in many-body systems to experimental scrutiny, such as examining what happens if the interaction and kinetic energies of particles are quenched across a quantum phase transition. The advances of this unique perspective are now reciprocating back to condensed matter problems where interaction of THz radiation on femtosecond timescales is also revealing correlated coherent electrons motion in solid-state systems. This topic of strongly-correlated many-body dynamics is the final strand of CCPQ development - embodied by the TNT project which introduces new ways of compressing many-body states to overcome the exponential barrier. It will support not only the emerging quantum technology of cold-atom quantum simulation, but also may eventually aid in designing and controlling real materials where optical pulses can switch properties such as superconductivity or ferroelectricity with great technological potential. CCPQ supports the development of these world leading community codes by providing a forum for the exchange of ideas, by providing networking opportunities for researchers to help disseminate the codes, and by supporting training workshops for users of the codes. It also provides direct support in the form of computer experts at the Daresbury laboratory who help optimise the codes for use on large high performance computers (HPC).

Astrophysically small molecules exist not just in quiescent cool clouds, which themselves are weakly ionized and therefore contain electrons, but also in much more active astrophysical regions such as planetary nebulae and diffuse interstellar clouds. These regions often contain significant numbers of free, quasi-thermal electrons, up to 10-4 compared to H2. These electrons can effect chemical change and drive observable spectroscopy processes (see A.J. Lim, I. Rabadan and J. Tennyson, MNRAS, 306, 473 (1999) for example); the cross sections between electrons and molecular ions are particularly large. Additionally electron molecule collisions are important elsewhere, for example they are the main driver behind planetary aurorae and many molecular masers. Models of all these regimes require data which is largely unknown and, in many cases, cannot be determined from laboratory based measurements. Over the last two decades the UCL group has developed the UK molecular R-matrix codes to provide a first principles, quantum mechanical treatment of the collision between low energy electrons and small molecules. This code has been used to treat collisions leading to rotational excitation involving important astrophysical ions (see for example A. Faure and J. Tennyson, MNRAS, 325, 443 (2001), A. Faure, J.D. Gorfinkiel and J. Tennyson, MNRAS 347, 323 (2004)). Recent observations of molecular emissions from C-shocked regions of the ISM (Jimenez-Serra et al, ApJ 650, L135 (2007)) showed that it is possible to recover local electron densities by using our electron molecule collisions calculations. Low-energy electrons also destroy molecules through dissociative recombination (DR for ions) and dissociative attachment (DA for neutrals). Cross sections for these processes are often hard to obtain. The present proposal is for a PhD student who will use the QuantemolN implementation of the UK polyatomic R- matrix code to study electron collisions with molecules of astrophysical interest and obtain dissociative cross sections. To do this the student will develop and test an add-on DA/DR estimator for Quantemol-N. A preliminary DA estimator developed by the company will provide the starting point for this work. The QuantemolN code, which will be provided by the company, is very suitable for these studies since it is an expert system which greatly increases the ease and speed with which a user can perform very technically demanding electron collision calculations. In return the student will assist the company in adding further features to this code to treat DA and DR. This project is proposed now since this feature has recently been requested by a Japanese industrial client of the company and a number of other users have expressed a strong interest. Adding to this functionality of the code is a strategic aim of Quantemol. The student will be provided training in performing electron molecule collision calculations, interpreting the results and using them in astronomical models and to interpret astronomical spectra. S/he will interact with people directly observing the processes, several of whom (for example Dr J Rawlings and Dr S Viti) are at UCL. S/he will also experience working with a small start up company which gives the opportunity to be involved both in the software development and in the interaction with other users of the code. This proposal follows a highly successful CASE studentship award to Dr HN Varambhia who used Quantemol-N to do studies on HCN, HNC, CS, CO and other astrophysically important systems (Eg Varambhia et al, Electron-impact rotational excitation of the carbon monosulfide (CS) molecule, MNRAS in press) which has been of immense benefit to the company by raising its scientific profile which led to new orders for the existing Quantemol-N package and interest in the others, from both the UK and abroad. Varambhia also added an electron impact ionization estimator to Quantemol-N.

This proposal concerns a novel type of photovoltaic (PV) solar cell. The threat of global warming is one reason for the rapid expansion in this low-carbon technology. In recent years, world-wide, solar cell manufacturing has been increasing exponentially by 47% each year. The development of higher efficiency cells will help this expansion continue. The Imperial Quantum Photovoltaic Group (QPV) have been collaborating with the EPSRC National Centre for III-V Technologies on an EPSRC grant GR/S81933 which has developed a novel, nano-structured solar cell known as the strain-balanced quantum well solar cell (SB-QWSC). Their primary achievement was to demonstrate a cell which operates at a 27% efficiency which is approximately twice the efficiency of the current Si based PV cells and close to the single junction cell efficiency record of 27.8%. The SB-QWSC is made from GaAs based alloys using the quantum well (QW) technology which underpins modern communication devices such as the laser, LED and the amplifier in mobile phones. The rapid PV market expansion has lead to a silicon feed-stock shortage, so cells based on a different material system and production technology are important if the expansion is to be maintained. As GaAs based cells are expensive a number of companies are developing light-concentrating systems, in which lenses or mirrors focus sunlight onto the cells. This way it is possible to reduce the area of the expensive PV cell by about 1/500. This leads to a major price reduction. The QWs give the cell a wider spectral range without introducing crystal dislocations. Both features give the SB-QWSC a number of advantages in concentrator applications over the tandem or triple junction GaAs based cells which were designed for use in space. The absence of dislocations means the SB-QWSC will have a longer device lifetime than the highest efficiency version of the multi-junction cell. At the same efficiency a SB-QWSC will outperform a conventional tandem cell because it does not require a tunnel junction to connect the cells. The wider spectral range of the QW cell results in significantly more electrical energy being harvested over a year due to the seasonal and daily spectral variation of the sunlight. The QPV group have also demonstrated that when the SB-QWSC is incorporated in a tandem cell the wider spectral range leads to a higher cell efficiency. This enhancement is such that in Madrid, where there is a guaranteed price for PV electricity fed into the grid, the energy savings are as large as the system capital cost over the anticipated 25 year lifetime. In the course of project GR/S81933 the QPV group unexpectedly observed that the SB-QWSC was exhibiting a phenomenon known as photon recycling when operating at high concentration. They had already demonstrated that the quantum well material was of such good quality that the only loss mechanism which operates at high light levels was the unavoidable loss of the current carriers back into photons of light. They observed that, when a mirror, known as a distributed Bragg reflector (DBR) is grown under the quantum wells, some of these lost photons are reflected back into the QWs. Here they are absorbed like the incident sunlight, add to the current and enhance the efficiency. The aim of this project is to study this effect further and see if it can be exploited commercially. We will investigate the use of deeper QWs, different DBRs and transparent substrates to maximise the effect in both single-junction and tandem cells. The maximum efficiency gain which might be achieved is ~ 4%, which is similar to that discussed above, i.e. giving savings similar to the system cost in a sunny location with a guaranteed price for PV electricity. This project should provide very significant added value to the second generation products of or our new company QuantaSol and also strengthen the intellectual property.

The dynamics of quantum particles is the basis to describing the material world. Collisions between nuclei provides basic chemical reactivity, while the movements of electrons around nuclei provides the fine mechanistic details. To understand these motions we need to solve the time-dependent Schroedinger equation - a non-trivial problem for more than 3 particles that requires a huge computational effort. State-of-the art experiments using attosecond or femtosecond pulses of radiation allow us to follow the motion of these particles, but without computer simulations the results are difficult to understand. This field of research is presently undergoing a huge expansion, due to the provision of new light sources such as free electron lasers (FELs), and software needs to be developed to keep up to the new capabilities. CCPQ has two community codes (R-matrix suite, MCTDH wavepacket dynamics) to treat these processes. The results give a deep inside into the fundamental reactivity of molecules, where quantum mechanical behaviour must be considered. The interactions of anti-matter particles are also a topic of much interest, primarily due to the use of positrons in medical imaging, but also as a field of fundamental science in experiments such as the ALPHA project. Here, anti-matter particles are collided with normal matter and the different decay channels investigated. CCPQ is developing a code in collaboration with experimentalists to help understand the behaviour of these exotic sounding, but useful, particles. Going from few bodies to many-bodies introduces some of the most fascinating phenomena in physics, such as superfluidity, superconductivity and ferroelectricity. However, to directly simulate them also introduces an exponentially scaling overhead in computation effort with the system size. While usually the preserve of condensed matter systems such strongly-correlated physics, where particles behaviour collectively, are now accessible in controlled ways with cold-atoms trapped in optical lattices. This has opened up previously inaccessible coherent dynamics in many-body systems to experimental scrutiny, such as examining what happens if the interaction and kinetic energies of particles are quenched across a quantum phase transition. The advances of this unique perspective are now reciprocating back to condensed matter problems where interaction of THz radiation on femtosecond timescales is also revealing correlated coherent electrons motion in solid-state systems. This topic of strongly-correlated many-body dynamics is the final strand of CCPQ development - embodied by the TNT project which introduces new ways of compressing many-body states to overcome the exponential barrier. It will support not only the emerging quantum technology of cold-atom quantum simulation, but also may eventually aid in designing and controlling real materials where optical pulses can switch properties such as superconductivity or ferroelectricity with great technological potential. CCPQ supports the development of these world leading community codes by providing a forum for the exchange of ideas, by providing networking opportunities for researchers to help disseminate the codes, and by supporting training workshops for users of the codes. It also provides direct support in the form of computer experts at the Daresbury laboratory who help optimise the codes for use on large high performance computers (HPC).