Javier E. Hasbun

The simple harmonic oscillator ground state using a variational Monte Carlo method

A Monte Carlo method is used to evaluate the ground-state energy of a quantum particle in a harmonic oscillator potential. The use of a trial wavefunction illustrates the process by means of which the Monte Carlo method approximates with great accuracy the well known ground-state energy of a quantum mechanical harmonic oscillator. A FORTRAN program incorporating the numerical approach that is suitable for a personal computer is available in the PDF version of this article.

Investigation of laser fundamentals using a helium-neon laser

Using an open-frame helium-neon (He-Ne) laser and optical spectrum analyser, students performed several upper-division laboratory experiments investigating important concepts regarding laser fundamentals. Such experiments include cavity stability (mirror geometry and thermal effects), longitudinal and transverse modes, free spectral range, and mode sweeping. In this paper we discuss, in an elementary way, the experimental procedures and results obtained.

Damped motion of a charged particle in the presence of electric and magnetic fields

The classical motion of a charged particle in the presence of an electric and a magnetic field is studied with the inclusion of scattering. The scattering is included in the Lagrangian equations for the particle through the use of the Rayleigh dissipation function. The resulting equations for the motion are solved analytically as a function of time. The behaviour of the charged particle motion is strikingly different from the case without scattering. Finally, for completeness, a connection is made between the steady state results and the electronic conductivity and resistivity of a solid. Resumen. El movimiento de una particula cargada en la presencia de un campo electrico y magnetico es estudiado, incluyendo las colisiones de la cargada en el medio. El efecto de las colisiones se incluyen en las ecuaciones Lagrangianas del problema por medio de la function de Rayleigh. Las ecuaciones que resultan para el movimiento de la particula se resuelven analiticamente como funcion de tiempo. El comportamiento del movimiento de la particula cargada es notablemente diferente del caso que no incluye colisiones. Finalmente, la conexion se hace entre los resultados obtenidos y la conductibilidad electronica de un solido.

Broad absorption natural dye (Mondo-Grass berry) for dye sensitized solar cell

Two major drawbacks in dye-sensitized solar cells (DSSC) are the narrow spectral response and the short-term stability. Research on development of artificial dyes for a broad frequency response is a major field of research today. The work presented here shows a broad response with a natural dye extracted from a Mondo-grass (Ophiopogon japonicus) berry. Its range of sensitivity covers the entire visible region and its tail expands to the near infrared. This is a unique situation since many natural dyes containing anthocyanin or carotenoids strongly absorbed only below 600xa0nm. A TiO2 based electrode sensitized with Mondo grass berry dye DSSC was tested for its performance. An open circuit photovoltage of 495xa0mV and a short circuit photocurrent of 0.6xa0mA/cm2 were obtained under 1 sun illumination. The broad spectral response from 400 to 750xa0nm was observed for the Mondo-grass berry dye. A high fill factor of 71% was achieved but energy conversion efficiency was only 0.2% for the cell. Even though cell efficiency is low with this dye, the solar cells have exhibited better stability when compared with that of the Blackberry. The thin layer chromatography results indicate that Mondo-grass berryxa0dye contains a mixture of two or more chemical compounds belonging to both the anthocyanin and the carotenoid families.

X-ray spectroscopy study of local microstructures in CdSe quantum dots prepared by UV photolithography

Colloidal Quantum Dots (QD) are inexpensive inorganic semiconductor nanoparticles, which are suspended in a solution formed by simple wet chemical methods. However, a major challenge in developing practical optoelectronics devices using these QDs is the difficulty of incorporating them into device structures. Cadmium Selenide (CdSe) QDs are synthesized using cadmium perchlorate hexahydrate and selenourea salts as precursors and 1-thioglycerol as a capping agent and patterned using UV photolithographic techniques on glass substrates. By changing UV light exposure time between 30 – 60 minutes, the size of QDs is found to be formed around 10u2005nm to 14u2005nm. With this technique, CdSe QDs and CdSe QDs/polymer matrix systems are grown on glass substrate and their local microstructure is investigated by using X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) methods. For the polymer, polyvinylcarbazole (PVK) is used. Three QD samples investigated are CdSe/Glass with 6...