She took a problem that had started in Calcutta — why chlorinated hydrocarbons quench the fluorescence of anthracene — to Oxford in 1950, wrote it up as a doctorate in 1952, and came home to start systematic photochemistry in India. The memoir this page rests on says the idea in the thesis later became the electron-transfer reaction of an excited molecule.
She was born in Patna into a joint family that had moved to Calcutta generations earlier, the second child, and grew up with six brothers and five sisters. The memoir says her father, a chemistry student who did not finish his MSc and became a businessman, set up a library and a chemistry laboratory in the house, and that her parents had the children trained in music and painting: she became an expert sitar player (p.113). She passed Matriculation in 1939 and the Intermediate of Science in 1941 at Ashutosh College, with distinction in chemistry; took her BSc with honours in chemistry at Scottish Church College in 1943, standing first among the women candidates in science; and her MSc in physical chemistry at Calcutta in 1945, first class, second in order of merit (pp.113–114).
In 1948 she began research at Jadavpur, at the College of Engineering and Technology, under Sachindra Nath Mukherjee, who gave her the subject: the fluorescence of anthracene in solution, and its quenching by chlorinated hydrocarbons. The memoir says the topic held her interest for the whole of her research career. She joined E. J. Bowen at Oxford in 1950 and took the DPhil in 1952, with a thesis the memoir titles Photochemistry of Anthracene Derivatives; it adds that she remained a Senior Member of St Anne’s College afterwards (p.114). Of the years after her return it says that systematic photophysics and photochemistry was hardly introduced in India in the early fifties and that she started it there, with the instruments and light sources available (p.115).
| Year | Where | What | Memoir |
|---|---|---|---|
| 1924 | Patna | born, 2 August | p.113 |
| 1943–45 | Calcutta | BSc honours (Scottish Church College); MSc physical chemistry, first class | p.114 |
| 1948 | Jadavpur | research begins under S. N. Mukherjee: anthracene fluorescence and its quenching | p.114 |
| 1950–52 | Oxford | with E. J. Bowen; DPhil 1952 | p.114 |
| 1954–56 | Calcutta | Sir P. C. Roy Research Fellow | p.114 |
| 1956 | Berkeley | Fulbright / Smith-Mundt grantee; lifetimes of excited molecules by a phase-shifting technique | p.114 |
| 1958 | Jadavpur | Reader in physical chemistry | p.114 |
| 1963–64 | IIT Kanpur | Assistant Professor, one year | p.114 |
| 1973–74 | JNU, New Delhi | Visiting Scientist, School of Life Sciences, one year | p.114 |
| 1974 | Jadavpur | Professor | p.114 |
| 1979–82 | Jadavpur | Head of the Department of Chemistry, three years | p.114 |
| 1989 | Jadavpur | retires; INSA Senior Scientist 1990–93 | p.114 |
| 2009 | Nagpur | dies, 31 December | p.123 |
The first of the memoir’s research highlights is this one (p.115). The problem taken up at Oxford under Bowen had been started in India and was carried out “more systematically and quantitatively” as a doctoral project. The reaction between anthracene and chlorinated hydrocarbons in deoxygenated solutions led to the concept of excited-state electron-transfer reactions. The memoir says the initial idea was in the thesis and was later firmly established by Naqvi, Ware, Carrol (as the memoir spells it), Whitten and others. With oxygen present, anthracenes photoperoxidise in halocarbon solvents, and the memoir says the intermediate is singlet oxygen, made when ground-state oxygen interacts with a triplet photosensitiser.
What the memoir does not give: which chlorinated hydrocarbons, what concentrations, what rates, what products, or how much of the thesis survives in the later literature. It names four later workers and gives no citation to any of them. The statement that the thesis contained the “initial idea” of excited-state electron transfer is the memoir’s own, written by a colleague; no search of the literature was made for this page, so it is repeated and not endorsed, and the page makes no priority claim for her.
Three things in the memoir’s account are checkable without the thesis. They are worked below as our derivations, with a script that fails if the algebra is wrong. They are not her results, and the memoir does not say she used these forms.
1 · Quenching. Let an excited molecule decay at rate k0 = 1/τ0 and be quenched by a species Q at rate kq[Q]. Under steady illumination the excited population is G/(k0 + kq[Q]) and the emission is proportional to it, so
I0/I = 1 + kq τ0 [Q]
a straight line in [Q] with slope kqτ0, not kq. The script integrates the decay numerically and checks it.
2 · The twist angle of a dimer. The memoir says the ratio of the transition-moment integrals of the two split bands of a dye dimer is a function of the angle θ between the two main oscillators (p.116). For two identical point transition dipoles of length μ at angle θ in a plane, the in-phase and out-of-phase combinations have dipoles μ√2 cos(θ/2) and μ√2 sin(θ/2), so the band intensities are 2μ²cos²(θ/2) and 2μ²sin²(θ/2):
sum = 2μ² (conserved) · ratio = cot²(θ/2) or its reciprocal, by which band is called which · θ = 2 arctan √r
At θ = 0 all the intensity sits in one band and nothing splits visibly; at θ = 90° the bands are equal. This is the point-dipole exciton model, a simplification the memoir does not state she used.
3 · Which term drives dimerisation. The memoir reports dimerisation constants and ΔG, ΔH and ΔS, and says dimer formation by fluorescein at pH 12 is enthalpy-directed while for rhodamines and halofluoresceins it is entropy-directed, through hydrophobic interaction (p.115). With ΔG° = −RT ln K and the van’t Hoff relation d ln K / d(1/T) = −ΔH/R, a set of K(T) values gives ΔH and then ΔS = (ΔH − ΔG)/T. Here we call a dimerisation enthalpy-directed if −ΔH is the larger contribution to −ΔG at the working temperature, and entropy-directed if TΔS is; the memoir gives no numbers and does not define the words this way. The script recovers a chosen ΔH and ΔS from synthetic data, and shows it can tell the two cases apart.
The memoir’s research highlights run to five items, the thesis problem above and then four more: the photophysics of laser dyes and their self-aggregation, with hypochromism and exciton interaction (pp.115–116); the photophysics and photochemistry of anthracene sulphonates, the water-soluble anthracenes, including singlet-oxygen generation (pp.116–117); photoelectrochemical conversion of light to electrical energy with porphyrins (pp.117–118); and the photochemistry of water-soluble porphyrins in organised media (p.118). Its claims about those results are its own and were not checked against the papers.
| Year | What | Memoir |
|---|---|---|
| 1964 | helps found the Indian Photobiology Group (later Society), affiliated to the Association Internationale de Photobiologie the same year | p.120 |
| 1966–68 | directs three consecutive summer institutes for college teachers, funded by the University Grants Commission and NSF/USAID | p.120 |
| 1978 | Fundamentals of Photochemistry (Wiley Eastern); revised edition 1986 | pp.122–123 |
| 1978 | flash photolysis with Sir George Porter at the Royal Institution, sponsored by the British Council | p.119 |
| c. 1980 | leads a departmental UGC project on conversion and storage of chemical energy | p.119 |
| Year | Office or honour | Memoir |
|---|---|---|
| 1980 | UGC National Lecturer; Vice-President, Indian Chemical Society | p.120 |
| 1984 | Fellow of the Indian National Science Academy | p.113 |
| 1985 | President, Chemistry Section, Indian Science Congress Association | p.120 |
| 1988 | President of the Tenth International Congress of Photobiology, Jerusalem; the memoir says the first from Asia; honorary member of the Association Internationale de Photobiologie the same year | pp.119–121 |
| 1990 | C. V. Raman Gold Medal, Indian Science Congress Association | p.114 |
She was married to Sushil Kumar Mukherjee, a chemist and former Vice-Chancellor of Calcutta and Kalyani Universities; the memoir says she had no children, and that she had suffered ill health and memory loss for the last ten years of her life (pp.121, 123).
Beyond the memoir, the author supplied her textbook, Fundamentals of Photochemistry (revised edition). Its Chapter 11, which begins on p.322, takes the reaction between anthracene and carbon tetrachloride as its case history (p.322). That is a neighbouring problem to the one in Part II, anthracene and a chlorinated hydrocarbon; whether it follows her thesis is not something this page can say, because the thesis was not read, and only the opening page of that chapter was read. Chapter 10, Tools and Techniques, is the basis of a branch of the gallery: the photochemistry instrument rooms, one each for light sources and actinometry, the spectrometer, the laser, and flash photolysis.
It does not assess any result. It rests on one source, an 18-page memoir by a former colleague, and the verify script checks that the page’s dates, names and page numbers are in that source and consistent with each other, not that the source is right. Four things are open.
The thesis itself was not read. It does not appear to be online; the file named for it in the author’s Downloads folder is this memoir. Every statement about what the thesis contained is the memoir’s.
Two sources disagree on the 1988 office. The memoir says she was President of the Tenth International Congress of Photobiology and was elected honorary member of the Association Internationale de Photobiologie that year. A web-encyclopaedia summary, seen only through an automatic summariser, says she was president of the Association itself from 1984 to 1988. They are not the same office, and this page follows the memoir.
The medal year. The memoir’s page image reads 1990, matching the encyclopaedia; one search summary gave 1991, which the page image does not support.
The Bowen paper. The memoir’s bibliography lists one paper with Bowen, Photochemistry of anthracene, Part II, in Faraday Society Discussions 14, 146. The year is lost in the scan’s text layer, the publisher’s page returned an access error, and the paper was not read.
Subhash Chandra Bera, Krishna Kamini Rohatgi-Mukherjee (2 August 1924 – 31 December 2009), Biographical Memoirs of Fellows of the Indian National Science Academy 38 (2010) 111–128,
supplied as a PDF with a scanned text layer containing recognition errors; key lines were read from the page images. Page numbers above are the memoir’s. · Web-encyclopaedia entry for her:
summary only, not read in full. · Checks: book7/ch-rohatgi-mukherjee-verify.py.
This chapter makes no claim about any present circumstances.