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 Majumder Group News

Research activities in 2021-22

During the summer and fall of the 2021-22 academic year, Charlotte Jones ’22 began her thesis work, and research assistants Russell Blakey ’23, Robin Wang ’24, and Abby Kinney ’24 also made important contributions. Postdoc John Lacy again took on an important leadership role, mentoring students, working closely along side them, and setting overall goals and agendas for the group. We are pursuing further high-precision transition amplitude measurements in the Pb system, using both a UV (368 nm) laser system, and a blue (406 nm) laser system.  As we have realized (and as Gabriel Patenotte further demonstrated in his thesis work last year (see below)), we can directly compare the observed absorptivity of hot Pb samples in vapor cells at two wavelengths – using the ground-state M1 transition (3P0 – 3P1, 1279 nm) as a normalization/reference as we originally did in our 2019 paper which appeared in PRA.

Interestingly, the excited-state E1 transitions (see energy level diagram above), which are 5-6 orders of magnitude ‘stronger’ than the ‘forbidden’ M1 and E2 transitions, happen to feature roughly comparable REDUCTION in signal strength due to the small Boltzmann factor associated with the excited states from which these E1 transitions originate.  As it turns out (see Patenotte thesis for example), at temperatures in the 800-900 C range, both excited state E1 transitions show absorptivity comparable in size to the forbidden ground-state transitions.  The challenge, then, is to accurately determine the sample temperature.  We are exploring encasing the quartz cells in stainless steel tubes, and mounting several special-purpose ‘S’ type thermocouples which have temperature accuracies quoted at +/- 1 degree Celsius at these temperatures.  This accuracy will be sufficient to allow an absolute transition amplitude measurement for the E1 transitions at the 1% level or better.

Prior to these measurements we are using the various lasers to measure isotope shifts (IS) and Pb-207 hyperfine splittings (HFS) using side-by-side cells in both dual transmission spectroscopy and dual Faraday spectroscopy setups.  We are completing the first direct IS and HFS measurements in the 939 nm transition, which are looking to be in good agreement with, and more precise than, indirect ‘inferred’ values from various older measurements of other nearby transitions.

We are pushing forward with a comprehensive re-measurement of both IS and HFS values in the 939 nm E2, 1279 nm M1, and 406 nm E1 transitions using careful calibration of our scans (via adding RF sidebands to FP transmission spectra) and then using those same scans to remove laser scan nonlinearities – something we have extensive experience with!  Charlotte’s 2022 thesis will include these spectroscopy results, as well as preliminary work towards the aforementioned 406/1279 transition amplitude comparison experiment using our Faraday polarimeter / vacuum furnace and a Pb-208 cell with accurate temperature monitoring.

Highlights of 2020-2021 academic year

In another challenging academic year with significant COVID-related restrictions, two class of ’21 thesis students completed impressive work in collaboration with postdoc John Lacy. We continued to focus on making measurements of atomic properties of multi-valence Group III and IV atomic systems.  This work currently centers on the Pb system, the first measurement of which was published in 2019.  

Patrick Postec ’21 developed and tested a new ‘heat pipe oven’ designed to provide the capability of higher temperatures and higher optical depth operation for future investigation of particularly weak transitions in Pb and potential Sn (another Group IV system).   Patrick took a position at Americorps for 2021-22, and has now completed applications to start a Ph.D. program in mechanical engineering which will focus on alternative energy and sustainability.

Gabriel Patenotte ’21 completed several years of association with our group, having designed, constructed, and optimized a new UV diode laser system that operates near zero degrees (Celsius) to reach the 368 nm (6p2) 3P1 –> (6p7s) 3P0 (E1) transition in Pb.  This laser now routinely outputs 10 mW of power and can scan single mode over nearly 20 GHz at this transition wavelength.  Gabriel also completed a preliminary (but very promising) comparative absorptivity measurement of this E1 transition in Pb compared to the ground-state M1 transition (whose QM linestrength is very accurately known).  Finally, he completed substantial atomic structure and modeling calculations to look at the Stark shift and Faraday rotation details of an atomic-beam-based measurement of Pb polarizability in this excited E1 transition. Gabriel is now in his first year as a Ph.D. student in the physics department at Harvard, pursuing cold-molecule science in the Ni group.  He joins recent Majumder group members Abdullah Nasir ’20, Nathaniel Vilas ’17, and Ben Augenbraun ’15 who all made a similar transition from Williams to AMO physics at Harvard.

Congratulations to both Patrick and Gabriel!  Here are these most recent theses:

Postec: “Towards the Measurement of the (6s2 6p2) 3P0–> 1D2 Forbidden E2 transitions in Lead via Faraday Rotation Spectroscopy Using a Heat Pipe Oven”

Patenotte: “Transition Polarizability and Amplitude Measurement of the Lead (6p2) 3P1 —> (6p7s) 3P0 Transition Using Faraday Rotation and Absorption Spectroscopy”

And here is the most recent group poster, given (virtually) at DAMOP 2021.

June 2020

Congratulations to Abdullah Nasir ’20 on his graduation.  It’s been a pleasure having him as part of our lab team, starting with a summer after his freshman year, and now culminating with excellent thesis work, especially in this crazy year in which much less was possible in the lab physically. We look forward to having him around for a little longer this summer, and then wish him the very best of luck at Harvard where he will be starting in the physics Ph.D. program this fall.

Here is his thesis:   Nasir_Thesis

We are also participating in virtual DAMOP 2020, and have prepared this poster:  DAMOP2020 Poster

And, undaunted, we had our annual Ephs @ DAMOP gathering, which was exceptionally well-attended, with Williams graduates from 1966 to 2021 represented, as well as current and former Majumder group postdocs!

We look forward to a summer of productive, if still virtual work with incoming thesis students Gabriel Patenotte ’21, and Patrick Postec ’21.

May 2020

Its been quite a six months since the last update.  I want to salute the amazing work of postdoc John Lacy and thesis student Abdullah Nasir ’20, as well as junior Gabriel Patenotte ’21 who will be starting his thesis work this summer.  In a time of unprecedented disruption and crisis, all of the team members have remained focused, productive, and as optimistic and positive as possible.

Through the winter and early spring, we focused as a team on two projects :
(1) translating our Faraday Rotation Spectroscopy (FRS) technique to our atomic beam apparatus, and to completely rebuilding our source / furnace and vacuum system to accommodate a new Pb atomic beam source.
(2) optimizing design and testing the behavior of our new 368.5 nm UV diode laser system which operates slightly below zero (Celsius) and now allows routine single-mode tuning around the Pb (6s2 6p2) 3P1 –> (6s2 6p7s) 3P0 E1 transition, which we have observed in a vapor cell.

Next steps as of March were to optimize the beam operation, and search for M1 FRS signals in the ABU. With the arrival of COVID-19, we went into a more virtual, shutdown mode.  John and Abdullah have been focusing both on a series of theory / simulation problems associated with measuring Polarizability (static E-field) in the presence of magnetic field necessary for FRS, as well as studying the small tensor polarizability component of the 3P1 state.

We look forward to a slow return to lab work soon.

November 2019

Welcome to our new postdoc, Dr. John Lacy, who arrived at the beginning of November from the UK, where he recently completed his D.Phil. at U. Sussex, having earlier done his Bachelors degree at Cambridge Univ.  John did his doctoral work in the area of development of novel electron Penning traps.  He is quickly integrating himself into all Majumder lab projects, working closely with Abdullah Nasir ’20 (thesis student) and Gabriel Pattenote ’21 and Declan Smith ’21 (research students) on both vapor cell and atomic beam experiments.

Our latest Pb Faraday spectroscopy work, completed in collaboration with theory co-authors Marianna Safronova and Sergey Porsev, has appeared in Physical Review A:

We are working to extend this high-precision polarimetry technique to the atomic beam environment, for spectroscopy and polarizability measurement in Lead, and also for precise isotope shift / HFS work in a ‘double polarimeter’ setup using our lead furnace.

June 2019

We have settled in to our new lab in the South Science Building.  This year saw completion of our Lead transition amplitude / Faraday polarimetry measurement, led by postdoc Dan Maser.  This work, with Safronova group co-authors, is being written up now.

Sophomores Gabriel Pattenote ’21 and Sameer Khanbhai ’21 continued their work with our group throughout the year.  Gabriel and Dan designed, constructed, and successfully tested a new UV laser system (368.5 nm) with which we did preliminary excited-state spectroscopy of Pb atoms in a cell.  Abdullah Nasir ’20 returned to the group to work over WSP in January, and will begin his senior thesis work in the Majumder lab this summer pursuing Pb atomic beam spectroscopy experiments.  He will be joined by rising juniors Declan Smith ’21 and Duncan McCarthy ’21 this summer.


vapor cell furnace and polarimetry                    ABU reincarnated in new lab!

May 2019

Tiku and Dan attended the 50th annual DAMOP meeting in Milwaukee, WI at the end of May.  Dan presented a 10-minute talk on our Pb quadrupole transition amplitude measurement.  PPT slides here:

We also presented a poster on this and upcoming work in the group:

We caught up with many recent alums!

Justin Brown ’05, Nathan Schine ’13, Ben Augenbraun ’15, Allison Carter ’16, Nathaniel Vilas ’17, Prof. Charlie Doret ’02, Tori Borish ’12

Majumder group alums @ DAMOP 2019
(L-R): Charlie Doret ’02 (Asst Prof @ Williams), Ben Augenbraun ’15, Dr. Dan Maser (Asst. Prof @ Conn College), Nathaniel Vilas ’17, Nathan Schine ’13, Allison Carter ’16

April 2019

Congratulations to Postdoc Dan Maser, who has accepted a tenure-track faculty position at Connecticut College in New London, CT!!  Dan will be building up a new lab to do laser spectroscopy of trace atmospheric molecules using frequency-comb technology.  We will truly miss Dan’s energy, expertise, and leadership in the group, but wish him the very, very best in his new adventure!

June 2018

Looking forward to unpacking and setting up our experiments in our brand new lab, Room 006 of the South Science Building, with Postdoc Dan Maser, and research assistants Gabe Pattenote ’21, and Sameer Khanbhai ’21.

Postdoc Dan Maser and thesis student Bingyi Wang ’18 attended the annual DAMOP meeting, as well as the precision measurement workshop that preceded it, in Fort Lauderdale, FL.  Here is a .pdf of the poster that they presented on our recent Indium polarizability measurements, including our latest results published in February.
DAMOP poster_2018 (1.6 MB)

Congratulations to Bingyi Wang ’18, who graduated magna cum laude & Phi Beta Kappa, on June 3rd, an is headed to Stanford this fall.  Here is her thesis:
Bingyi_Wang_Thesis(3.4 MB)

February 2018

Congratulations to Bingyi Wang ’18, current thesis student, for being chosen as one of the inaugural cohort of  Knight-Hennessey Scholars at Stanford University, where she will be beginning in the Physics Ph.D. program.  Bingyi was one of 50 scholars out of several thousand applicants!

February 2018

Our latest Indium atomic beam polarizability measurements have been published, with Marianna Safronova’s group contributing ab initio calculations, so that for the first time we can systematically compare two side-by-side calculational methods (the so-called Coupled Cluster method and the Configuration Interaction / All-order method).  Our latest results for the polarizability of the 7p states and earlier results for the 6p and 6s states show clear ‘preference’ for the latter theory method for the case of these excited states in this trivalent atom.

Co-authors from our group are Nathaniel Vilas ’17, Bingyi Wang ’18, and recent and current postdocs Milinda Rupasinghe and Dan Maser.

October 2017

We are very happy to welcome new postdoc Dr. Daniel Maser to our group.  Dan completed his undergraduate degree at Berkeley, and his Ph.D. at the Univ. of Colorado, working in Scott Diddams’ lab at NIST building new frequency-comb-based mid-IR laser sources for sensing applications.

Dan will immediately join current thesis student Bingyi Wang ’18 as we complete our latest indium ABU polarizability experiment, and also continue our Pb transition amplitude / Faraday polarimetry work begun last year by Eli Hoenig ’17.

DAMOP 2017, Sacramento, CA June 5-9, 2017

A great week in Sacramento with lots of current and former students and colleagues!

Current Majumder group attendees:  Nathaniel Vilas ’17, Eli Hoenig ’17, Postdoc Milinda Rupasinghe,  Joined by Prof. Charlie Doret, three of his students, and Prof. Swati Singh.

     Receiving APS Prize w/current DAMOP chair Steve Rolston.

   At poster session with Nathaniel and Eli

  Ephs @ DAMOP 2017

  Current, former Majumder lab thesis students in attendance:
(L-R)  Eli Hoenig ’17, Nathaniel Vilas ’17, Nathan Schine ’13, Colin Bruzewicz ’05, Ben Augenbraun ’15, Charlie Doret ’02

Here are the posters we presented on the Pb and In experiments:
Pb Faraday spectroscopy / E2 transition measurement
In atomic beam polarizability measurements

May 2017

Congratulations to Eli Hoenig ’17 and Nathaniel Vilas ’17 who completed their senior theses describing excellent work and exciting new results in two experiments:

Nathaniel Vilas – two-step atomic beam spectroscopy / polarizability measurements of the indium 7p states:  Vilas Thesis (4 MB)

Eli Hoenig – Lead vapor cell polarimetry of both the 1279 nm M1 and 939 nm E2 transitions to measure absolute transition linestrengths:  Hoenig Thesis (6 MB)

February 2017

We have resurrected our optical polarimeter, with plans to measure the M1 and E2 ground-state transition amplitudes in Lead (comparing Faraday Rotation signals for a common magnetic field and in the same vapor cell) to test new atomic theory calculations.  Some pretty impressive measurements (thanks Eli!) of intrinsic angle noise at the 0.1 μradian / √Hz level:

Angle noise test with 940 nm laser

October 2016

Received this exciting news in a letter from the APS this week:

On behalf of the American Physical Society, it is my pleasure to inform you that you have been awarded the 2017 Prize for a Faculty Member for Research in an Undergraduate Institution:

“For contributions to the precision measurement of atomic properties, and sustained, inspirational mentorship of undergraduate researchers.”

This could not have happened without an institution committed to supporting research with undergraduates, as well as great colleagues, and, most of all, a wonderful and talented collection of Williams students with whom I’ve had the privilege of working for the past 20 years.  I’m very grateful!

Summer 2016

Group picture from summer (L-R:  Nathaniel Vilas ’17, PKM, Eli Hoenig ’17, Bingyi Wang ’18)

Rising thesis students Eli Hoenig ’17, Nathaniel Vilas ’17, as well as rising junior Bing Yi Wang ’18 and postdoc Milinda Rupasinghe completed a series of vapor cell spectroscopy experiments in thallium and indium using our two-step spectroscopy technique.  All the second-step transitions were in the red 650-690 nm range and so by exchanging diodes we measured hyperfine structure and isotope shifts all with sub-MHz accuracy.  This work is now being written up for publication.

Meanwhile, our paper describing the latest atomic beam polarizability measurement (in the indium 6p1/2 excited state) was published in Phys. Rev. A  in August with Ben Augenbraun ’15 and Allison Carter ’16 as co-authors.

June 2016

Congratulations to Allison Carter ’16, and Sauman ’16 who graduated on June 5th, and completed very successful senior thesis projects in the lab this year!  Good luck to Allison, who is starting in the Physics Ph.D. program at U. Maryland, and to Sauman, who is starting in the Mech. Eng. Ph.D. program at U. Colorado this fall.  We will miss you!


This year’s theses:
Allison:  indium 6p1/2 state polarizability measurement  using the atomic beam (2.7 MB)
Sauman:  thallium 8p1/2-state HFS/ IS shift work using the heated vapor cell  (8.4 MB)


Oh — and something to make me feel old:  Picture of my very first set of thesis students who returned this June for their 20th reunion!! (Kyle Downey ’96, Paul Boerner ’96):

DAMOP 2016, May 23-27 2016, Providence, RI

The proximity of this year’s DAMOP conference allowed Profs. Doret and Majumder to fill up a van with Ephs and drive.  Accompanying them were graduating seniors Allison Carter ’16, Sauman Cheng ’16, and Ariel  Silbert ’16.  Also attending were Nathaniel Vilas ’17 and Sierra Jubin ’17, who will be starting thesis work this summer, and also postdoc Milinda Rupasinghe.

Ben Augenbraun ’15 attended the conference, and formally received his 2015 APS Apker Award certificate, and gave an excellent invited talk on his thesis work.

Many other Ephs (19 in all!) were in attendance (spanning more than a half century of graduating classes!):


Here are all of the current and former Majumder group thesis students in attendance:


(L-R) Allison Carter ’16 (U. Maryland), Nathaniel Vilas ’17, Sauman Cheng ’16 (U. Colorado), Ben Augenbraun ’15 (Harvard), Charlie Doret ’02 (Harvard, GTRI, Williams!), PKM, Colin Bruzewicz ’05 (Yale, Lincoln Labs), Nathan Schine ’13 (U. Chicago), Paul Hess ’08 (Harvard, U. Maryland).

And here we are at the poster session with our two group posters behind:


PDFs of posters presented:
Indium 6p1/2-state Atomic Beam / Stark shift measurement
Thallium 8p/12-state HFS/IS spectroscopy
October 2015

Congratulations to thesis student Ben Augenbraun ’15 who is the 2015 A.P.S. LeRoy Apker Award  WINNER !!! (the Apker Award is the nation’s top honor for undergraduate physics research).  We wish Ben the very best as he begins in the Ph.D. program at Harvard this fall.  

Former group member, and now Williams physics department colleague, Charlie Doret ’02 was the 2002 Apker Award winner.  All together FIVE Williams physics majors have won this award.

Here is a link to Ben’s undergraduate thesis:
Augenbraun thesis (6.2 MB)

June, 2015

We welcome Sauman Cheng ’16 and Allison Carter ’16 to the lab this summer , who will begin their thesis work, and will be joined by Nathanial Vilas ’17, Milinda, and Prof. Majumder.

Here is a picture of the summer 2015 research group:


DAMOP 2015, Columbus, OH:
Ben Augenbraun ’15, Postdoc Milinda Rupasinghe, and Prof. Majumder attended the 2015 DAMOP conference in Columbus, OH.  Here are some highlights:

Ben Augenbraun ’15, Nathan Schine ’13 and PKM in front of latest group poster on two-step, atomic beam Stark shift experiment in Indium.

[email protected] 2015: (L-R) Ben Augenbraun ’15,Dr. Justin Brown ’05 (Draper Labs), Paul Hess ’08 (Harvard, JQI), Colin Bruzewicz ’05 (Yale, Lincoln Labs),Prof. Charlie Doret ’02 (Harvard, Williams College), Dr. Milinda Rupasinghe (postdoc, Majumder group),Nathan Schine ’13 (U. Chicago),Ryan Carollo ’05 (U. Conn), Prof. Chad Orzel ’93 (Union College), PKM, Prof. Josh Grossman ’96 (St. Mary’s College)

Former Majumder group thesis students @ DAMOP: Paul Hess ’08 (Harvard), Ben Augenbraun (Harvard), Charlie Doret (Harvard), Nathan Schine (Chicago), Colin Bruzewicz (Yale)

Winter/Spring, 2015
Welcome to new postdoc, Dr. Milinda Rupasinghe, who joined us in January from Oklahoma, where he did his Ph.D. work in atomic physics.

 We gratefully acknowledge the support of our new 3-year NSF grant #1404206 which supports our postdoc, summer studies, and equipment and supply needs.


DAMOP 2014, Madison, WI:
Here is the latest from our group, including recent photos, DAMOP 14 conference posters, senior honors theses, and publications    

[email protected] 2014: (L-R) Prof. Chad Orzel ’93 (Union College), Prof. Josh Grossman ’96 (St. Mary’s College), Prof. Charlie Doret ’02 (Williams College), PKM, Nathan Schine ’13 (U. Chicago), Dr. Justin Brown ’05 (Draper Labs), Ryan Carollo ’05 (U. Conn), Ben Augenbraun ’15

Nathan Schine ’13 (now at U. Chicago) and Ben Augenbraun ’15 at Poster Session w/indium atomic beam poster, DAMOP 14.

POSTERS FROM DAMOP 2014, Madison, WI, June 2-5
Atomic Beam / Stark shift poster  (2.8 MB)
Vapor Cell / 2-step Spectroscopy poster (3.8 MB)



  • Senior Honors Thesis of Allison Carter ’16 (now at U. Maryland): Carter thesis (2.7 MB)
  • Senior Honors Thesis of Ben Augenbraun ’15 (now at Harvard Univ.):  Augenbraun thesis (6.2 MB)
  • Senior Honors Thesis of Nathan Bricault ’14 (now at Cambridge Univ): Bricault_thesis
  • Senior Honors Thesis of Nathan Schine ’13 (Simon group, U. Chicago):   Schine_thesis

Phys. Rev. A paper describing this work:



  • Senior Honors Thesis of Sauman Cheng ’16 (now at U. Colorado): Cheng thesis 
  • Senior Honors Thesis of Gabby Vukasin  ’14 (now at Stanford Univ):     Vukasin_thesis
  • Senior Honors Thesis of David Kealhofer ’13 (now at UCSB):    Kealhofer_thesis

 Phys. Rev. A paper describing this work: