arXiv subjects

T. Madhu Trivikram

Publications and source records attributed to T. Madhu Trivikram.

3 recordsLinked to original sources

arXiv2018

Relativistic and QED effects in the fundamental vibration of T$_2$

The hydrogen molecule has become a test ground for quantum electrodynamical calculations in molecules. Expanding beyond studies on stable hydrogenic species to the heavier radioactive tritium-bearing molecules, we report on a measurement of the fundamental T$_2$ vibrational splitting $(v= 0 \rightarrow 1)$ for $J=0-5$ rotational levels. Precision frequency metrology is performed with high-resolution coherent anti-Stokes Raman spectroscopy at an experimental uncertainty of $10-12$~MHz, where sub-Doppler saturation features are exploited for the strongest transition. The achieved accuracy corresponds to a fifty-fold improvement over a previous measurement, and allows for the extraction of relativistic and QED contributions to T$_2$ transition energies.

physics.chem-ph↗

arXiv2016

Precision measurements and test of molecular theory in highly-excited vibrational states of H$_2$ $(v=11)$

Accurate $EF{}^1Σ^+_g-X{}^1Σ^+_g$ transition energies in molecular hydrogen were determined for transitions originating from levels with highly-excited vibrational quantum number, $v=11$, in the ground electronic state. Doppler-free two-photon spectroscopy was applied on vibrationally excited H$_2^*$, produced via the photodissociation of H$_2$S, yielding transition frequencies with accuracies of $45$ MHz or $0.0015$ cm$^{-1}$. An important improvement is the enhanced detection efficiency by resonant excitation to autoionizing $7pπ$ electronic Rydberg states, resulting in narrow transitions due to reduced ac-Stark effects. Using known $EF$ level energies, the level energies of $X(v=11, J=1,3-5)$ states are derived with accuracies of typically 0.002 cm$^{-1}$. These experimental values are in excellent agreement with, and are more accurate than the results obtained from the most advanced ab initio molecular theory calculations including relativistic and QED contributions.

physics.atom-ph↗

arXiv2016

Spectroscopy and perturbation analysis of the A$^1Π$(v=0) state of $^{13}$C$^{16}$O

The lowest $v=0$ level of the A$^1Π$, state of the $^{13}$C$^{16}$O isotopologue of carbon monoxide has been reinvestigated with a variety of high resolution spectroscopic techniques. The A$^1Π-$X$^1Σ^+(0,0)$ band has been studied by vacuum-ultraviolet Fourier-transform absorption spectroscopy, using the SOLEIL synchrotron as a radiation source. Spectra were obtained under quasi-static gas conditions at liquid-nitrogen temperature, room temperature and at an elevated temperature of 900 K, with absolute accuracies of 0.01$-$0.03 cm$^{-1}$. Two-photon Doppler-free laser spectroscopy has been applied to a limited number of transitions in the A$^1Π-$X$^1Σ^+(0,0)$ band, under collision-free circumstances of a molecular beam, yielding an absolute accuracy of 0.002 cm$^{-1}$. The third technique is high-resolution Fourier-transform emission spectroscopy in the visible region applied to the B$^1Σ^+-$A$^1Π(0,0)$ band in a gas discharge, at an absolute accuracy of up to 0.003 cm$^{-1}$. With these methods rotational levels of A$^1Π(0)$ could be studied in both parity components up to a rotational quantum number of $J=46$. The frequencies of 397 transitions were used to analyse the perturbations between the A$^1Π(0)$ level by vibrational levels of the D$^1\!Δ$, e$^3Σ^-$, d$^3\!Δ$, and a$'^3Σ^+$ states.

physics.atom-ph↗