Professor Howard R. Reiss passed away at the age of 93
On August 25, 2022, Professor Howard R. Reiss passed away at the age of 93. For the past 18 years, Prof. Reiss has worked at the MBI, which had become his scientific base. His scientific carrier spanned over 70 years. His seminal 1962 paper, „Absorption of light by light,“ arguably initiated the field of relativistic quantum electrodynamics in intense laser fields, which today is being experimentally pursued, e.g., by the „Extreme Light Infrastructure (ELI)“. He used the nonrelativistic version of his theoretical framework for the first thorough description in 1980 of above-threshold ionization (ATI), which provided a foundation for today's attosecond science, the latest offspring of strong-field physics.
Life in Strong Laser Fields
In Loving Memory of Professor Howard Reiss
My Lord, while the Earth is still spinning,
My Lord, while the sun is still bright,
Eternal, be kind and give everyone,
whatever they pray for at night:
Help old sage get wiser,
grant coward the fastest horse,
give contented money…
And don’t forget humbly yours.
From “The Prayer of Francois Villon” by Bulat Okudzhava, translated from Russian by M. Ivanov
“This thing all things devours: birds, beasts, trees, flowers; gnaws iron, bites steel; grinds hard stones to meal; slays king, ruins town, and beats high mountain down,” – thus spoke Gollum to Bilbo Baggins, and “time” was the answer to his riddle. Time shows no mercy, and late this August, 2022, it has beaten down the high mountain of Professor Howard Reiss.
For the past 18 years, the Max Born Institute for Nonlinear Optics has been his home in more ways than one, as science was Howard’s life. Howard came to the MBI in 2004 as a guest scientist and as one of the founders of the field of multiphoton and strong field processes in intense light fields. He was well into his seventies already then, but his energy and tenacity in arguing his physics views was still second to none, and it remained this way until his last days. He was 93 years old.
In 2004, he was already a living legend. After all, Howard’s 1962 paper [1] together with his seminal 1980 paper [2] are at the roots of this field. His vision of how one could – no, must – describe atoms and electrons interacting with very intense light fields has been instrumental for its development. His visit to the Soviet Union in 1962, when he managed to tunnel through the newly erected Iron Curtain while being the Chief of the Nuclear Physics Division at the US Naval Ordnance Lab was extraordinary not just because of this highly improbable tunneling event. While in Moscow, he argued how one should – no, must – treat intense light-matter interaction, and his lectures might have stimulated the explosive development of the theory of intense field processes in the Soviet Union in 1960-th [3-9]. Already then, Howard’s approach was fully relativistic, taking roots in his earlier work [10-11], well beyond the non-relativistic treatments of intense light-atom interactions that have become standard later, and that are now used by everyone working in the field, me including (1).
Armed with the relativistic vision, for the last two decades Howard has persistently argued that non-dipole effects should be important for strong-field ionization in long-wavelength fields. In this, as in other cases, he was not afraid to go against the common wisdom. His stand was difficult, as he was arguing against the time-tested truth engraved in every textbook on light-matter interaction: the longer the laser wavelength, the better is the dipole approximation, the smaller are the non-dipole effects. Howard argued the opposite [12-13]. It must have been very rewarding for him to see that his view, rooted in a general mathematical perspective, has found physical confirmation in several recent experiments [14-18]. The physical basis for this seemingly counter-intuitive fact is the rapidly growing quiver velocity of the electron liberated from the atom and wiggling in the laser field: the quiver velocity scales linearly with the laser wavelength. In the highly popular today mid-IR fields, this velocity does indeed become non-negligible compared to the speed of light at the laser intensities I~ 1014W/cm2, heralding the onset of the Lorenz force and of the non-dipole effects in rather typical experimental conditions.
Going back in time, I have been amazed to discover that already in 1977 Howard was working on what has now become the forefront of the field: strong field processes in solids [19]. The application of his method to solids [19], together with the work of Keldysh [3], lied dormant until Ref. [20] started the boom in 2011, with an avalanche of research to follow.
Going back in time… time travel is not really required for the so-called “butterfly effect”, when the death of a butterfly in the past, brought on by a careless time traveler, irrevocably changes the future. Trajectories of our lives are indeed altered by chance events. At the turn of this century, the Fates brought Wilhelm Becker and Howard Reiss to the then-young MBI, turning it into one of the world centers for the theory of intense light-matter interaction and laying the first seeds for the major part of the MBI science landscape today. Looking further into the past – who knows if Leonid Keldysh would have written his seminal paper [3] without being stimulated by Howard’s visit? And if he did not, the theory landscape of strong-field physics in Soviet Union might have never been the same, I might have never chosen this field for my career, and the Fates might have never brought me to the MBI.
I vividly remember meeting the legendary Howard for the first time about 30 years ago. He has been an imposing figure, in physics and in physical presence. A mere beginner, I approached him with trepidation, only to discover an open and charming person. Intense in science, in life Howard was gentle, a true gentleman, an amazing companion and interlocutor. Besides science, his interests covered art, history, politics, music, prose and poetry. He held well-informed views on any subject we would raise. Without him, not just our lunches but also our days will never be the same. And if this sounds too personal for an obituary, how could it be otherwise when a Legend that one had the privilege to meet on any given day passes away?
Misha Ivanov, September 9, 2022
[1] Personally, I have never mastered the fully relativistic treatment, and never will.
References
[1] Reiss, Howard R. "Absorption of light by light." Journal of Mathematical Physics 3.1 (1962): 59-67.
[2] Reiss, Howard R. "Effect of an intense electromagnetic field on a weakly bound system." Physical Review A 22.5 (1980): 1786.
[3] Keldysh, L. V. "Ionization in the field of a strong electromagnetic wave." Sov. Phys. JETP 20.5 (1965): 1307-1314.
[4] Perelomov, A. M., V. S. Popov, and M. V. Terent’Ev. "Ionization of atoms in an alternating electric field." Sov. Phys. JETP 23.5 (1966): 924-934.
[5] Perelomov, A. M., Popov, V. S., & Terent’ev, M. V. (1967). Ionization of atoms in an alternating electric field: II. Sov. Phys. JETP, 24(1), 207-217.
[6] Perelomov, A. M., and V. S. Popov. "Ionization of atoms in an alternating electrical field. ill." Sov. Phys. JETP 25.2 (1967).
[7] Popov, V. S., V. P. Kuznetsov, and A. M. Perelomov. "Quasiclassical approximation for nonstationary problems." Sov. Phys. JETP 26 (1968): 222.
[8] Nikishov, A. I., and V. I. Ritus. "Ionization of systems bound by short-range forces by the field of an electromagnetic wave." Sov. Phys. JETP 23.1 (1966): 168-177.
[9] Nikishov, A. I., and V. I. Ritus. "Ionization of atoms by an electromagnetic-wave field." Sov. Phys. JETP 25.1 (1967): 145.
[10] Reiss, Howard R., and Joseph H. Eberly. "Green's function in intense-field electrodynamics." Physical Review 151.4 (1966): 1058.
[11] Reiss, Howard R. "Production of electron pairs from a zero-mass state." Physical Review Letters 26.17 (1971): 1072.
[12] H. R. Reiss, “Limits on tunneling theories of strong-field ionization,” Phys. Rev. Lett. 101, 043002 (2008).
[13] H. R. Reiss, “The tunnelling model of laser-induced ionization and its failure at low frequencies,” J. Phys. B: At., Mol. Opt. Phys. 47, 204006 (2014).
[14] Nida Haram, et al, “Relativistic nondipole effects in strong-field atomic ionization at moderate intensities,” Phys. Rev. Lett. 123, 093201 (2019).
[15] A. Hartung, el at, “Magnetic fields alter strong-field ionization,” Nature Physics 15, 1222–1226 (2019).
[16] A. Hartung, et al, “Electric nondipole effect in strong-field ionization,” Phys. Rev. Lett. 126, 053202 (2021).
[17] N. Haram, R. T. Sang, and I. V. Litvinyuk, “Transverse electron momentum distributions in strongfield ionization: nondipole and coulomb focusing effects,” J. Phys. B: At., Mol. Opt. Phys. 53, 154005 (2020).
[18] J. Maurer and U. Keller, “Ionization in intense laser fields beyond the electric dipole approximation: concepts, methods, achievements and future directions,” J. Phys. B: At., Mol. Opt. Phys. 54, 094001 (2021)
[19] Jones, H. D., & Reiss, H. R. (1977). Intense-field effects in solids. Physical Review B, 16(6), 2466.
[20] S. Ghimire, et al. "Observation of high-order harmonic generation in a bulk crystal." Nature physics 7.2 (2011): 138-141.