arXiv subjects

P. K. Majumder

Publications and source records attributed to P. K. Majumder.

8 recordsLinked to original sources

arXiv2025

High-precision measurements of electric-dipole-transition amplitudes in excited states of $^{208}$Pb using Faraday rotation spectroscopy

We have completed measurements of two low-lying excited-state electric-dipole (E1) transition amplitudes in lead. Our measured reduced matrix elements of the $(6s^2 6p^2)^3P_1 \to (6s^2 6p7s)^3P_0$ transition at 368.3 nm and the 405.8 nm $(6s^2 6p^2)^3P_2 \to (6s^2 6p7s)^3P_1$ transition are 1.90(1) a.u. and 3.01(2) a.u. respectively, both measured to sub-1 % precision and both in excellent agreement with the latest $ab \ initio$ lead wavefunction calculations. These measurements were completed by comparing the low-field Faraday optical rotation spectra of each E1 transition in turn with that of the ground-state $^{3}P_0 \to ^{3}P_1$ M1 transition under identical experimental conditions. Our spectroscopy technique involves polarization modulation and lock-in detection yielding microradian-level optical rotation resolution. At temperatures where direct absorption was significant for both E1 and M1 transitions, we also extracted matrix element values from a direct optical absorption depth comparison. As part of this work we designed an interaction region within our furnace which allowed precise determination of our quartz vapor cell sample temperature to provide accurate determination of the Boltzmann thermal population of the low-lying excited states that were studied.

physics.atom-ph↗

arXiv2019

High-precision measurement and ab initio calculation of the $(6s^26p^2)\,^3\!P_0 \rightarrow \, ^3\!P_2$ electric quadrupole transition amplitude in $^{208}$Pb

We have completed a measurement of the $(6s^26p^2)\, ^3\!P_0 \rightarrow \, ^3\!P_2$ 939 nm electric quadrupole ($E2$) transition amplitude in atomic lead. Using a Faraday rotation spectroscopy technique and a sensitive polarimeter, we have measured this very weak $E2$ transition for the first time, and determined its amplitude to be $\langle ^3\!P_2 || Q || ^3\!P_0 \rangle$ = 8.91(9) a.u.. We also present an ab initio theoretical calculation of this matrix element, which agrees with experiment at the 0.5\% level. We heat a quartz vapor cell containing $^{208}$Pb to between 800 and 940 $^{\circ}$C, apply a $\sim \! 10 \, {\rm G}$ longitudinal magnetic field, and use polarization modulation/lock-in detection to measure optical rotation amplitudes of order 1 mrad with noise near 1 $μ$rad. We compare the Faraday rotation amplitude of the $E2$ transition to that of the $^3\!P_0 -\, ^3\!P_1$ 1279 nm magnetic dipole ($M1$) transition under identical sample conditions.

physics.atom-ph↗

arXiv2017

High-precision measurements and theoretical calculations of indium excited-state polarizabilities

We report measurements of the $^{115}$In $7p_{1/2}$ and $7p_{3/2}$ scalar and tensor polarizabilities using two-step diode laser spectroscopy in an atomic beam. The scalar polarizabilities are one to two orders of magnitude larger than for lower lying indium states due to the close proximity of the $7p$ and $6d$ states. For the scalar polarizabilities, we find values (in atomic units) of $1.811(4) \times 10^5$ $a_0^3$ and $2.876(6) \times 10^5$ $a_0^3$ for the $7p_{1/2}$ and $7p_{3/2}$ states respectively. We estimate the smaller tensor polarizability component of the $7p_{3/2}$ state to be $-1.43(18) \times 10^4$ $a_0^3$. These measurements represent the first high-precision benchmarks of transition properties of such high excited states of trivalent atomic systems. We also present new ab initio calculations of these quantities and other In polarizabilities using two high-precision relativistic methods to make a global comparison of the accuracies of the two approaches. The precision of the experiment is sufficient to differentiate between the two theoretical methods as well as to allow precise determination of the indium $7p-6d$ matrix elements. The results obtained in this work are applicable to other heavier and more complicated systems, and provide much needed guidance for the development of even more precise theoretical approaches.

physics.atom-ph↗

arXiv2017

Measurement of hyperfine splittings and isotope shifts in the $8p$ excited states of $^{205}$Tl and $^{203}$Tl using two-step laser spectroscopy

A two-step, two-color laser spectroscopy technique has been used to measure the hyperfine splittings of the $8p$ excited states in $^{203}$Tl and $^{205}$Tl, as well as the $7s - 8p$ transition isotope shifts. For the case of the $8p_{3/2}$ state, our results show a hyperfine anomaly consistent with our recent measurements of other hyperfine splittings, and in disagreement with older results for this state. Our measurement of the $8p_{1/2}$ isotope shift is also in disagreement with earlier work. In this series of experiments, a UV laser was locked to the first-step transition and directed through a heated vapor cell, while a second spatially overlapping red laser was scanned across the two second-step transitions. To facilitate accurate frequency calibration, radio-frequency modulation of the second-step laser was used to create sidebands in the Doppler-free absorption spectrum.

physics.atom-ph↗

arXiv2016

Measurement of the scalar polarizability of the indium $6p_{1/2}$ state using two-step atomic-beam spectroscopy

We have completed a measurement of the Stark shift within the $^{115}$In $6s_{1/2} \rightarrow 6p_{1/2}$ excited-state transition using two-step laser spectroscopy in an indium atomic beam. Combining this measurement with recent experimental results we determine the scalar polarizability, $α_{0}$, of the $6p_{1/2}$ state to be $7683 \pm43 \,a_{0}^{3}$ in atomic units, a result which agrees very well with recent theoretical calculations. In this experiment, one laser, stabilized to the $5p_{1/2} \rightarrow 6s_{1/2}$ 410~nm transition, was directed transversely to the atomic beam, while a second, overlapping laser was scanned across the 1343~nm $6s_{1/2} \rightarrow 6p_{1/2}$ transition. We utilized two-tone frequency-modulation spectroscopy of the infrared laser beam to measure the second-step absorption in the interaction region, where the optical depth is less than 10$^{-3}$. In the course of our experimental work we also determined the hyperfine splitting within the $6p_{1/2}$ state, improving upon the precision of an existing measurement.

physics.atom-ph↗

arXiv2013

Measurement of 7p$_{1/2}$-state hyperfine structure and 7s$_{1/2}$-7p$_{1/2}$ transition isotope shift in $^{203}$Tl and $^{205}$Tl

A two-step, two-color laser spectroscopy technique has been used to measure the hyperfine splitting of the 7p$_{1/2}$ excited state in $^{203}$Tl and $^{205}$Tl, as well as the isotope shift within the 7s$_{1/2}$ - 7p$_{1/2}$ transition. Our measured values for the hyperfine splittings, 2153.2(7) MHz (in $^{203}$Tl) and 2173.3(8) MHz (in $^{205}$Tl), each differ by 20 MHz from previously published values which quoted comparable precision. The transition isotope shift of $^{203}$Tl relative to $^{205}$Tl was measured to be 534.4(9) MHz. In our experiment, one laser was locked to the thallium ground-state 6p$_{1/2}$ - 7s$_{1/2}$ 378 nm transition, while the second, spatially overlapping laser was scanned across the 7s$_{1/2}$(F=1) - 7p$_{1/2}$(F=0,1) hyperfine transitions. To facilitate accurate frequency calibration, radio-frequency modulation of the laser was used to create sidebands in the absorption spectrum.

physics.atom-ph↗

arXiv2013

Thallium 7p lifetimes derived from experimental data and ab initio calculations of scalar polarizabilities

Two different theoretical methods have been used to complete a new calculation of polarizability in the thallium 6p_{1/2}, 7s, and 7p_{1/2} states. The predictions of the two methods agree to within 1% for the 6p_{1/2} and 7s states and 2% for 7p_{1/2} state. We find that the theoretical expression for the 6p_{1/2} - 7s transition polarizability difference is dominated (greater than 90% contribution) by mixing of the 7s state with the 7p_{1/2} and 7p_{3/2} states. By comparing the theoretical expression to an existing Stark shift measurement [Doret et al., Phys. Rev. A 66, 052504 (2002)], new, highly-accurate values for the thallium 7p excited-state lifetimes have been extracted. The scalar polarizability of the 7p_{1/2} state is also computed, anticipating an experimental determination of this quantity, which will then enable a high-precision determination of the 6d_{j}-7p_{j^{\prime}} transition rates and provide a benchmark test of the two theoretical approaches in the near future.

physics.atom-ph↗

arXiv2013

Measurement of the scalar polarizability within the 5P1/2-6S1/2, 410 nm transition in atomic indium

We have completed a new measurement of the Stark shift in 115In within the 410 nm 5P1/2- 6S1/2 transition. We measure the Stark shift constant to be kS= - 122.92(33)kHz/(kV/cm)^2, corresponding to a difference in the 6S1/2 and 5P1/2 state polarizabilities, Δα_0, of 1000.2 (2.7) a.u.(in atomic units). This result is a factor of 30 more precise than previous measurements and is in excellent agreement with a new theoretical value based on an ab initio calculation of the wave functions in this three-valence-electron system. The measurement was performed in an indium atomic beam apparatus, used a GaN laser diode system, and exploited an FM spectroscopy technique to extract laser transmission spectra under conditions where our interaction region optical depth was typically less than 10^-3.

physics.atom-ph↗