arXiv subjects

Pranav R. Shirhatti

Publications and source records attributed to Pranav R. Shirhatti.

6 recordsLinked to original sources

arXiv2023

A versatile and narrow linewidth infra-red radiation source for ro-vibration state selected preparation of molecules in molecular beams

We describe the design and characterization of a versatile pulsed (5 ns, 10 Hz repetition rate) optical parametric oscillator and amplifier system capable of generating single longitudinal mode, narrow linewidth (0.01 cm$^{-1}$) radiation in the wavelength range of 680 - 870 nm and 1380 - 4650 nm. Using a combination of power-normalized photoacoustic signal and a Fizeau interferometer-based wavemeter, we are able to actively stabilize the output wavenumber to within 0.005 cm$^{-1}$ (3$σ$) over a timescale longer than 1000 seconds. We demonstrate an application of this system by performing ro-vibration state-selected preparation of CO in v = 2 state, via direct overtone excitation (v = 0 $\rightarrow 2$ at 2346 nm) and subsequent state-selected detection in an internally cold molecular beam.

physics.optics↗

arXiv2023

The curious case of CO$_2$ dissociation on Cu(110)

Dissociation of CO$_2$ on copper surfaces, a model system for understanding the elementary steps in catalytic conversion of CO$_2$ to methanol has been extensively studied in the past. It is thought to be reasonably well-understood from both experiments and theory. In contrast, our findings reported here suggest a different picture. Using molecular beam surface scattering methods, we measure the initial dissociation probabilities ($S_{\rm 0}$) of CO$_2$ on a flat, clean Cu(110) surface under ultra-high vacuum conditions. The observed $S_{\rm 0}$ ranges from $3.9\times10^{-4}$ to $1.8\times10^{-2}$ at incidence energies of 0.64 eV to 1.59 eV with a lower limit to dissociation barrier estimated to be around 2.0 eV, much larger than that understood previously. We discuss the possible reasons behind such large differences in our results and previous work. These findings are anticipated to be extremely important for obtaining a correct understanding of elementary steps in CO$_2$ dissociation on Cu surfaces.

physics.chem-ph↗

arXiv2023

A compact and highly collimated atomic/molecular beam source

We describe the design, characterization and application of a simple, highly collimated and compact atomic/molecular beam source. This source is based on a segmented capillary design, constructed using a syringe needle. Angular width measurements and free molecular flow simulations show that the segmented structure effectively suppresses atoms travelling in off-axis directions, resulting in a narrow beam of Helium atoms having a width of 7 mrad (full width half maximum). We demonstrate an application of this source by using it for monitoring real-time changes in surface coverage on a clean Cu(110) surface exposed to oxygen, by measuring specular reflectivity of the Helium beam generated using this source.

physics.chem-ph↗

arXiv2022

Contrast inversion in neutral atom microscopy using atomic cluster beams

This work explores the possibility of atomic cluster beams as a probe for neutral atom microscopy (NAM) measurements. Using a beam of Kr clusters with mean size $\sim$ 10$^4$ atoms/cluster we demonstrate that topographical contrast can be obtained, similar to that in the case of monoatomic beams. Further, using atomically thin films of MoS$_2$ grown on SiO$_2$/Si substrate we show that NAM imaging using Kr clusters is also possible in domains where topographical contrast is not expected. Surprisingly, these images show an inverted contrast pattern when compared to the case of monoatomic beams. We attempt to understand these observations on the basis of angular distributions resulting from cluster-surface scattering. Finally, we discuss the implications of these results towards achieving a high lateral resolution neutral atom microscope using atomic cluster beams.

physics.chem-ph↗

arXiv2022

A simple and low-cost setup for part per billion level frequency stabilization and characterization of red He-Ne laser

This work describes the frequency stabilization of a dual longitudinal mode, red (632.8 nm) He-Ne laser, implemented using a low-cost microcontroller and its performance characterization using a simple interferometric method. Our studies demonstrate that frequency stability up to 0.42 MHz (3$σ$, 17 hours) can be achieved using this set up. This simple and low-cost system can serve as an excellent part per billion level frequency reference for several high resolution spectroscopy based applications.

physics.ins-det↗

arXiv2022

Neutral atom scattering based mapping of atomically thin layers

Imaging surfaces using low energy neutral atom scattering is a relatively recent development in the field of microscopy. In this work we demonstrate that this technique is sensitive enough to distinguish films as thin as a single monolayer from the underlying substrate. Using collimated beams of He and Kr atoms as an incident probe on MoS$_2$ films grown on SiO$_2$/Si substrate, we observe systematic changes in the scattered atom flux which allows us to map the thin MoS$_2$ films. Measurements carried out by varying incidence energy using both He and Kr provides insights into the details of atom-surface collision dynamics and its role in contrast generation.

physics.chem-ph↗