The year 2020 was an unusual year in many respects. Most people will remember it as the year of the SARS-Cov-2 (Covid-19) pandemic. The global uncertainty posed by the situation eventually led to the 2020 joint European Conference On Nonlinear Optical Spectroscopy (ECONOS) and European CARS Workshop (ECW), which was scheduled to be held in Karlsruhe/Germany in April, to be cancelled at rather short notice. Under normal circumstances, this would imply that there would not be a special issue in JRS. However, in the beginning of 2020, the ECONOS/ECW community learnt that one of its most inspiring members and a dear friend to many of us, Marcus Motzkus, sadly passed away after suffering from severe illness. Therefore, we decided to organize a special issue anyway to highlight Marcus's role and contributions.

Marcus was born in Berlin in 1966. He studied geophysics and geology in Berlin and physics at RWTH Aachen before he joined the Max Planck Institute for Quantum Optics in Garching near Munich for his PhD studies, where he came into contact with nonlinear optical spectroscopy. In 1994, he earned his PhD from the Ludwig-Maximilians-University of Munich based on his thesis on the development and application of four-wave mixing techniques for the investigation of reactive and non-adiabatic collisional processes in gases. After that, he did a postdoc in Ahmed Zewail's group at the California Institute of Technology, where he worked in the field of femtosecond spectroscopy, before returning to the Max Planck Institute for his habilitation. He completed the latter with a thesis on the coherent control of ultrafast molecular quantum processes in 2002. In 2003, he was appointed as professor of physical chemistry at the Philipps-University Marburg. Eventually, Marcus moved to Heidelberg in 2009, where he became chair professor of physical chemistry at the University of Heidelberg.

Marcus's research interests included the development and application of nonlinear time-domain spectroscopy and nonlinear optical microscopy as well as the coherent control of ultrafast molecular processes using shaped laser pulses. Over many years, his work had substantial impact on the ECONOS/ECW community, and mentioning all his achievements would certainly go beyond the scope of this editorial. To highlight only a few, the long list includes the development of femtosecond CARS of hydrogen,^[1] which became a pioneering piece of work in the field of combustion diagnostics with ultrafast lasers. His work on the quantum control of energy flow in light harvesting^[2] also received much attention as it demonstrated that the concept of coherent control can be applied to a highly complex process such as photosynthesis. Microspectroscopy is another scientific area, in which Marcus has made substantial contributions, especially over the last decade. In particular, the development of multimodal microscopy approaches using shaped femtosecond pulses for the analysis of tissue^[3] is noteworthy.

Since his PhD studies, Marcus was connected to the topics of ECONOS/ECW. He rarely missed any of the meetings and showed a strong dedication to our particular conference for over more than two decades. With his frequent invited talks and contributions, he truly shaped the meetings and delivered memorable highlights. Therefore, it is no surprise that so many groups associated with ECONOS/ECW immediately committed to contribute to this special issue,^[4-20] which happens to be the largest collection of papers in this annual series in more than a decade.

Marcus passed away far too early, and the community misses him sadly. We will always remember him as a valued colleague, outstanding scientist and dear friend.

2020年在很多方面都是不寻常的一年。大多数人会记得那是 SARS-Cov-2 (Covid-19) 大流行的一年。局势带来的全球不确定性最终导致原定于 4 月在德国卡尔斯鲁厄举行的 2020 年欧洲非线性光谱学联合会议 (ECONOS) 和欧洲 CARS 研讨会 (ECW) 在相当短的时间内取消. 在正常情况下，这意味着JRS 中不会有特殊问题。然而，在 2020 年初，ECONOS/ECW 社区得知其最鼓舞人心的成员之一，也是我们许多人的挚友 Marcus Motzkus，在患重病后不幸去世。因此，我们决定无论如何都组织一个特刊来突出 Marcus 的角色和贡献。

Marcus 1966 年出生于柏林。在加入位于慕尼黑附近加兴的马克斯普朗克量子光学研究所攻读博士学位之前，他在柏林学习地球物理学和地质学，并在亚琛工业大学学习物理学，并在那里接触到非线性光谱学。1994 年，他获得了慕尼黑路德维希马克西米利安大学的博士学位，论文是四波混合技术的发展和应用，用于研究气体中的反应性和非绝热碰撞过程。之后，他在加州理工学院的 Ahmed Zewail 小组做博士后，在那里他从事飞秒光谱学领域的工作，然后返回马克斯普朗克研究所获得资格。2002 年，他以一篇关于超快分子量子过程的相干控制的论文完成了后者。2003年，他被任命为菲利普斯大学马尔堡物理化学教授。最终，马库斯于 2009 年搬到海德堡，在那里他成为海德堡大学物理化学讲座教授。

Marcus 的研究兴趣包括非线性时域光谱学和非线性光学显微镜的开发和应用，以及使用整形激光脉冲对超快分子过程进行相干控制。多年来，他的工作对 ECONOS/ECW 社区产生了重大影响，提及他的所有成就肯定超出了本社论的范围。仅举几个例子，长长的清单包括氢飞秒 C​​ARS 的开发，^{[ 1 ]}成为使用超快激光器进行燃烧诊断领域的开创性工作。他在光收集中能量流的量子控制方面的工作^{[ 2 ]}也受到了很多关注，因为它表明相干控制的概念可以应用于高度复杂的过程，例如光合作用。显微光谱学是另一个科学领域，马库斯在其中做出了重大贡献，尤其是在过去十年中。特别是，使用成形飞秒脉冲进行组织分析的多模态显微镜方法的发展^{[ 3 ]}是值得注意的。

自攻读博士学位以来，Marcus 与 ECONOS/ECW 的主题相关。二十多年来，他很少错过任何一次会议，并表现出对我们特定会议的强烈奉献精神。他频繁的受邀演讲和贡献，真正塑造了会议并提供了令人难忘的亮点。因此，毫不奇怪，这么多与 ECONOS/ECW 相关的团体立即承诺为这个特刊做出贡献，^{[ 4-20 ]}这恰好是十多年来这个年度系列中最大的论文集。

马库斯过早地去世了，社区非常怀念他。我们将永远记住他，他是一位重要的同事、杰出的科学家和亲爱的朋友。